Continuous closed-circuit seawater desalination device

Abstract

The invention relates to a device (2) for treating water by reverse osmosis comprising: - at least one reverse osmosis membrane unit configured to extract a permeate from water to be desalinated, - at least one conduit for supplying water to be treated (8) to the membrane unit, - at least one outlet conduit (16) for a concentrate from the membrane unit, - at least one reservoir (24), - at least one conduit (26) for discharging the concentrate to the reservoir (24), - at least one conduit for recharging the reservoir (24) with water to be treated, characterized in that the reservoir (24) comprises a first connection (52) fluidly connected to the conduit (26) for discharging the concentrate and a second connection (54) fluidly connected to the conduit for sending the water to be treated (32) and hydraulic members (40, 41) for rectifying the concentrate flow velocity field lines and / or water to be treated (52, 54). Figure for abstract: figure 1

Description

Title of the invention: Device for continuous desalination of seawater in a closed circuit

[0001] The invention relates to devices for treating water to be treated, and more particularly to devices for treating seawater in a closed circuit.

[0002] It is known to desalinate seawater by reverse osmosis. Desalination by reverse osmosis occurs when a salt water solution is compressed against semi-permeable membranes at a water pressure greater than the osmotic pressure of the water. This pressure difference is the driving force behind the reverse osmosis seawater desalination process. Currently, the conventional reverse osmosis configuration consists of feeding one or more pressure tubes in parallel with seawater, the pressure tube(s) being composed of several membrane modules arranged in series. Seawater is fed under pressure at the head of the pressure tube, flows through the membrane modules in series and exits at the other end of the pressure tube. Under the effect of the water pressure, only water passes through the semi-permeable reverse osmosis membranes while the salts are retained.The water that passes through the membrane, called permeate, is desalinated. The flow that has not passed through the membrane is called concentrate. The concentrate at the outlet of the first module becomes the feed for the second module and so on along the pressure tube. The water pressure allowing the water to pass through the membrane must be higher than the osmotic pressure, which depends in particular on the salt concentration. Osmotic pressure increases with the concentration of dissolved salts. As the seawater flows through the pressure tube, it becomes concentrated in salts, due to the extraction of non-saline water, which leads to an increase in osmotic pressure. Therefore, the highest osmotic pressure is found at the end of the pressure tube.The water pressure at the inlet of the pressure tube is therefore calculated to be higher than the osmotic pressure at the end of the pressure tube in order to be able to extract water along the entire length of the pressure tube.

[0003] Such operation generates significant energy consumption. Indeed, since the osmotic pressure is lower at the inlet of the pressure tube, the feed pressure of the first membranes could be lower in order to guarantee the driving force necessary for their production of permeate.

[0004] The concentrate extracted at the end of the pressure tube is always at a high pressure, corresponding to the feed pressure from which the pressure losses linked to the flow through the membrane modules are subtracted. This pressure Residual energy also represents a significant energy loss. In order to recover this energy, energy recovery equipment allows the pressure of the concentrate to be transferred to a portion of the seawater supplying the module(s) and thus reduces energy consumption. However, these systems remain expensive, which impacts the total cost of a seawater installation. In addition, the efficiency of these energy recovery installations is not 100%.

[0005] It is known, to overcome this drawback, to use a seawater desalination device, operating in a closed circuit by recirculating the concentrate at the feed level of the pressure tube(s) so that it passes through the pressure tube(s) several times. The recirculated flow is mixed with the continuous pressurized feed of fresh seawater which makes it possible to maintain the volume of the recirculation loop constant by compensating for the water loss linked to the production of permeate. Each time water passes through the pressure tube(s) (seawater or concentrate), the water pressure is adjusted in order to maintain the driving force constant and thus allow permeate production despite the gradual increase in the salinity of the seawater as the recirculation cycles progress.

[0006] Once the concentrate has reached a defined salt concentration and / or the feed pressure has reached the set value, and / or the system conversion rate has reached the desired value, the concentrate is discharged and replaced with fresh seawater to recharge the desalination circuit with raw seawater to be desalinated and start a new concentration cycle. This sequential operation leads to a reduction or even a stoppage of permeate production due to the aforementioned replacement because the pressure in the desalination device is significantly reduced during this purge step, which reduces the driving force applied and therefore the production of permeate. The frequency of recharging the desalination circuit depends on the concentration cycle duration, the salinity of the feed water, the permeate flow rate, the free volume in the recirculation loop or the recirculation flow rate.In the case of seawater desalination or concentrate treatment applications, the reloading frequency is high, so the loss of production during the concentrate purging steps is significant on the productivity of this process.

[0007] In order to overcome this loss of pressure, it is known to provide, in parallel with the concentrate recirculation loop, the presence of a parallel pipe equipped with one or more pressure tanks containing seawater connected to the recirculation loop. When the recirculation loop must be recharged with seawater, the concentrate is sent to the tank of the parallel pipe containing the fresh seawater at an identical pressure and expels the seawater stored inside the latter. The latter is sent into the recirculation loop, which allows to recharge the filtration device while evacuating the concentrate and this by adapting the water pressure to always apply a net driving pressure defined for the given permeate production and therefore maintaining the permeate production constant (the concentrate will be replaced by seawater for a new desalination cycle in parallel with the operation of the recirculation loop) and thus reduce the impact of recharging with seawater on the productivity of the whole.

[0008] However, when replacing the raw water with the concentrate in the parallel pipe, the two flows tend to mix at the interface of the two liquids. This results in an increase in the salinity of the seawater when a new cycle is restarted (which starts again with a little of the concentrate) and therefore a reduction in the efficiency of the process (higher water pressure when restarting because the osmotic pressure is also higher, shorter desalination cycle due to higher salinity of the seawater introduced into the recirculation loop from the tank).

[0009] The invention aims to remedy this by providing a device for continuous treatment of salt water in a closed loop having a parallel pipe and limiting the concentrate / water mixture to be treated.

[0010] To this end, the invention relates to a device for treating water to be treated by closed-circuit reverse osmosis comprising: - a reverse osmosis membrane unit configured to produce a permeate and a concentrate from the water to be treated, - at least one conduit for supplying the water to be treated to the reverse osmosis membrane unit, - at least one outlet pipe for the concentrate from the reverse osmosis membrane unit, - at least one conduit forming a recirculation loop and connecting the supply conduit for the water to be treated and the outlet conduit for a concentrate from the reverse osmosis membrane unit so as to allow a return of the concentrate to the reverse osmosis membrane unit, - at least one tank delimiting a storage volume, - at least one concentrate discharge pipe to the tank, from the concentrate outlet pipe of the reverse osmosis unit, and at least one concentrate extraction pipe from the tank, - at least one conduit for sending water to be treated stored in the tank to the conduit for supplying the water to be treated and at least one conduit for recharging the tank with water to be treated, the tank comprising a first tapping arranged so as to allow injection of concentrate into the tank and a second tapping arranged so as to to allow an injection of water to be treated into the reservoir, the reservoir comprising at least one first hydraulic member configured to straighten velocity field lines of a concentrate flow in the reservoir so as to make them substantially parallel to each other and parallel to a main extension direction of the reservoir, and at least one second hydraulic member configured to straighten velocity field lines of a water flow to be treated in the reservoir so as to make them substantially parallel to each other and parallel to the main extension direction of the reservoir.

[0011] This avoids the propagation of turbulent flows linked to the injection of concentrate and water to be treated inside the tank. The straightening of the limit velocity field lines even avoids the mixing between the concentrate and the water to be treated at the interface of the two liquids at the time of replacement of the water to be treated by concentrate, and vice versa.

[0012] According to other optional characteristics of the treatment device taken alone or in combination: - At least one of the first and second hydraulic members extends at a distance of between 0 and 25 cm from a first opening delimited by the first tapping or from a second opening delimited by the second tapping. - At least one of the first and second hydraulic members comprises a perforated plate extending inside the tank, - At least one of the first and second hydraulic members comprises a perforated pipe extending into the tank from a first opening delimited by the first tapping or from a second opening delimited by the second tapping, - At least one of the first and second hydraulic members extends substantially perpendicular to the main extension direction of the tank, - At least one of the first and second hydraulic members extends over at least 50% of a passage section of the tank, - The first tapping and / or the second tapping are arranged in the tank so as to inject the concentrate and / or the water to be treated in a direction parallel to a main extension direction of the tank, - At least one of the first and second hydraulic members is formed of a plurality of plates for straightening the flow velocity field lines of concentrate and / or water to be treated extending in directions substantially parallel to each other and to a main extension direction of the tank, - The tank is formed by at least one external envelope of a pressure tube, - The treatment device comprises several reservoirs fluidically connected in series, - The tanks are formed by external envelopes of pressure tubes connected in series, and - The treatment device comprises means for regulating the speed of entry of the concentrate and / or water to be treated into the tank.

[0013] The invention also relates to a method for treating water to be treated using a treatment device according to the invention, the treatment method comprising repeating, at least once, the following steps:

[0014] - a recirculation step in which the water to be treated circulates several times in the reverse osmosis membrane unit by passing through the recirculation loop,

[0015] - a purge step in which the concentrate is brought to the tank by the first tapping and water to be treated stored in the tank is sent to the supply pipe for the water to be treated by the second tapping, and

[0016] - a reloading step in which the concentrate is evacuated from the device of treatment by the first tapping and the tank is filled with water to be treated by the second tapping.

[0017] According to other optional characteristics of the treatment device taken alone or in combination: - The treatment method comprises a step of regulating the rate of entry of the concentrate and / or water to be treated into the tank, and - The concentrate and / or water to be treated moves in the tank at a speed between 0.04 and 0.5 m / s. Brief description of the figures

[0018] The invention will be better understood on reading the following description, given solely by way of example and with reference to the attached drawings, not to scale, in which:

[0019] [Fig-1] is a schematic representation of a processing device according to a first embodiment of the invention, during a concentrate recirculation step,

[0020] [Fig.2] is a schematic representation of a processing device according to the first embodiment of the invention, during a step of purging the treatment device,

[0021] [Fig.3] is a schematic representation of a treatment device according to the first embodiment of the invention, during a step of reloading the treatment device,

[0022] [Fig.4] is a schematic representation of a processing device according to a second embodiment of the invention,

[0023] [Fig.5] is a schematic representation of a portion of reservoir according to a first variant embodiment of the invention,

[0024] [Fig.6] is a schematic representation of a portion of reservoir according to a second variant embodiment of the invention,

[0025] [Fig.7] is a schematic representation of a portion of reservoir according to a third variant embodiment of the invention,

[0026] [Fig.8] is a schematic representation of a portion of reservoir according to a fourth variant embodiment of the invention, and

[0027] [Fig.9] is a flowchart of a treatment method according to the invention. Detailed description

[0028] Reference is now made to Figures 1 to 3 illustrating a treatment device 2 for water to be treated according to a first embodiment of the invention. The water treatment device 2 is a continuous desalination device, in the sense that it allows seawater to be desalinated continuously, and in a closed or semi-closed loop, in the sense that an initial volume of raw water to be treated will be treated several times, and that a replacement of the concentrate is carried out by adding a new volume of water to be treated from an additional tank.

[0029] The term "water to be treated" means seawater, brackish water or treated water from a treatment plant. More generally, it can be any water that can be treated by desalination (reduction of the ionic charge).

[0030] The treatment device 2 comprises a reverse osmosis unit which may comprise at least one first pressure tube 4 comprising at least one desalination module 6 (two in FIGS. 1 to 6) formed by at least one semi-permeable membrane, for example reverse osmosis, the pressure tube 4 being configured to extract a permeate from water to be desalinated, whether it is water to be treated or recirculated concentrate. The desalination modules 6 comprise semi-permeable membranes allowing water to pass through and retaining, among other things, the salt when the water pressure of the water passing through them is greater than the osmotic pressure of this water.The membranes of the different desalination modules 6 may be identical or have different permeabilities and / or rejection rates, for example: membranes with lower permeability may be used at the head of the pressure tube 4, and membranes with higher permeability at the end of the tube. pressure 4. A permeate extracted from the water to be desalinated is extracted from the treatment device 2 (arrow 3 in figures 1 to 6).

[0031] The treatment device 2 comprises at least one conduit 8 for supplying water to be treated to the reverse osmosis membrane unit. This conduit can be supplied with water to be treated by a feed pump 10. A first filter 12, for example a cartridge filter, can be placed downstream of the feed pump 10 in order to retain the impurities present in the raw seawater before the water to be treated enters the conduit 8 for supplying water to be treated, and this in order to limit the fouling of the treatment device 2, in particular of the reverse osmosis membrane unit.

[0032] At least one pressurizing member 14 (for example a high-pressure pump) is configured to increase the pressure of water passing through the water supply pipe to be treated 8 and the reverse osmosis membrane unit so as to obtain a water pressure greater than the osmotic pressure of the water passing through the reverse osmosis membrane unit. This pressurizing member 14 is placed, in the figures, downstream of the filter 12 and sends the water to be treated (raw water and / or concentrate) to the reverse osmosis membrane unit with sufficient pressure to allow desalination of the water passing through the pressure tube 4, at least at the head of the pressure tube 4. The treatment device 2 therefore comprises means for measuring the flow rate of permeate extracted from the treatment device 2 to be able to adjust the water pressure in order to ensure extraction of permeate while avoiding excessive energy consumption.More precisely, and after observing a reduction in the permeate flow rate, the flow rate of the pressurization member 14 is increased so as to increase the water pressure and thus ensure satisfactory permeate extraction by overcoming the production resistance, in particular the osmotic pressure.

[0033] The treatment device 2 comprises an outlet conduit 16 for the concentrate from the reverse osmosis membrane unit. This conduit may comprise a recirculation pump 18 for recirculating the concentrate or for evacuating it, as described below.

[0034] The treatment device 2 comprises at least one conduit forming a recirculation loop 20 connecting the supply pipe 8 for water to be desalinated and the outlet pipe 16 for a concentrate from the reverse osmosis membrane unit so as to allow a return of the concentrate to the latter. Thus, the concentrate leaving the reverse osmosis membrane unit and which can still be treated passes through the recirculation loop 20, is pressurized by the pressurization member 14 to a pressure allowing extraction of permeate from the water passing through the reverse osmosis membrane unit. A first valve 22, typically a pneumatic valve, is placed at the level of the recirculation loop 20 in order to allow or prohibit the recirculation of the concentrate through the recirculation loop and this depending on the achievement of a target for stopping the recirculation of the concentrate: achievement of a ceiling water pressure (for example equal to 60 bars), a predefined salinity of the concentrate, a predefined time interval, etc.

[0035] The treatment device 2 further comprises a reservoir 24 delimiting a storage volume, typically of water to be treated or concentrate. This reservoir 24 makes it possible to store seawater on standby during recirculation of the concentrate in the treatment device 2. When it is no longer relevant to recirculate the concentrate in the reverse osmosis membrane unit, the latter can be sent to the reservoir 24 to take the place of the water to be treated, which is in turn sent to the reverse osmosis membrane unit, as will be described later.

[0036] The treatment device 2 also comprises at least one conduit 26 for discharging the concentrate to the tank 24, from the concentrate outlet conduit 16 of the reverse osmosis membrane unit, and at least one conduit 26' for extracting the concentrate from the tank 24. These conduits make it possible to send the concentrate at the outlet of the reverse osmosis membrane unit to the tank 24 or to cause the concentrate to leave the treatment device 2 by extracting it from the tank 24. It comprises a second valve 28 and a third valve 30: - The second valve 28 placed on the conduit 26 for discharging the concentrate to the tank 24 and intended to have an open / closed state opposite to that of the first valve 22 and this in order to direct the concentrate leaving the reverse osmosis membrane unit via the recirculation loop 20 or towards the tank 24 thanks to the conduit for discharging the concentrate to the tank 24 and extracting the concentrate from the tank 24. - The third valve 30 present on the conduit 26' for extracting the concentrate from the tank 24 and which allows, when it is open, the concentrate to be extracted from the treatment device 2.

[0037] The treatment device 2 further comprises at least one conduit 32 for sending water to be treated stored from the reservoir 24 to the conduit 8 for supplying water to be treated and at least one conduit 32' for recharging the reservoir 24 with water to be treated. The conduit 32 for sending water to be treated stored from the tank 24 to the conduit for supplying water to be treated 8 allows, when the concentrate takes the place of seawater in the tank 24, to send the latter to the reverse osmosis membrane unit through the conduit for supplying water to be treated 8. It comprises a fourth valve 34 authorizing or prohibiting the passage of water to be treated from the conduit 32 for sending water to be treated stored from the tank 24 to the conduit for supplying water to be treated 8. The conduit 32' for recharging the tank 24 with water to be treated allows water to be treated to enter the treatment device 2 in order to recharge tank 24 with water to be treated and replacing the concentrate stored inside tank 24.

[0038] A refill pump 36, placed on the pipe 32' for refilling the tank 24 with water to be treated, is provided in order to refill the tank 24 with water to be treated as will be described later. A second filter 38, for example a cartridge filter, also makes it possible to prevent the entry of impurities present in the water to be treated entering the treatment device 2. Finally, an isolation pump 42 is placed downstream of the second filter 38 so as to allow communication between the pipe for refilling the tank with water to be treated 32' and the tank 24 (with closing of the fourth valve 34) when refilling the tank 24 with water to be treated and replacing the concentrate.

[0039] The reservoir 24 comprises a first tapping 52 arranged so as to allow an injection of concentrate into the reservoir 24 and at least one first hydraulic member 40 configured to straighten velocity field lines of a concentrate flow in the reservoir 24 so as to make them substantially parallel to each other and parallel to a main extension direction A (illustrated in FIGS. 1 and 4) of the reservoir 24.

[0040] The reservoir 24 further comprises a second tapping 54 arranged so as to allow an injection of water to be treated into the reservoir 24 and at least one second hydraulic member 41 configured to straighten velocity field lines of a flow of water to be treated in the reservoir 24 so as to make them substantially parallel to each other and parallel to the main extension direction A of the reservoir 24.

[0041] A certain linearization is therefore obtained in the movement of concentrate and / or water to be treated in the tank 24.

[0042] The first tapping is provided in a first wall 46, while the second tapping is made in a second wall 48. A side wall 50 connects the first and second walls 46 and 48.

[0043] The side wall 50 may advantageously be of the general shape of a cylinder of revolution.

[0044] Advantageously, the tank 24 is formed by an external casing of a pressure tube. In this case, the tank 24 may for example have the following dimensions: internal diameter of 202.2 millimeters, length equal to 1.5 meters. The flow rate of liquid in the tank 24 may be 8, 16 and 25 m3 / h, with a speed of movement of concentrate and / or water to be treated in the tank 24 of between 0.04 and 0.5 m / s.

[0045] The first tapping 52 delimits at least a first opening for the passage of the concentrate towards the storage volume of the tank 24. The second tapping 54 delimits at least a second opening for the passage of the water to be treated towards the storage volume of the tank 24.

[0046] The number of tappings made at the first and second walls 46 and 48 may be greater than a single tapping, in particular in the case where several tappings would allow better distribution of the concentrate and / or the water to be treated entering the tank 24.

[0047] In the first embodiment of the invention, the first tapping 52 and the second tapping 54 are arranged in the tank 24 so as to inject the concentrate and the water to be treated in a direction parallel to a main extension direction A of the tank 24. This makes it possible to avoid a rebound of the liquid which would be injected into the tank 24 from the side wall 50 and therefore to minimize the turbulence in the tank 24 at the time of said injection.

[0048] Advantageously, the hydraulic members 40 and 41 extend over at least 50% of a passage section of the reservoir 24. This makes it possible to obtain an effective action of the latter with respect to the flow of liquid passing through it.

[0049] Advantageously, at least one of the first or second hydraulic members extends at a distance of between 0 and 25 cm from a first opening delimited by the first tapping or from a second opening delimited by the second tapping.

[0050] As explained above, the treatment device 2 comprises several valves and pumps making it possible to obtain different operating configurations. More generally, the treatment device comprises a set of control members configured to obtain: - a recirculation configuration in which the water to be treated circulates several times in the reverse osmosis membrane unit by passing through the recirculation loop 20, - a purge configuration in which the concentrate is brought to the tank 24 by the first tapping 52 and water to be treated stored in the tank 24 is sent to the supply pipe for the water to be treated 8 by the second tapping 54, and - a recharging configuration in which the concentrate is evacuated from the treatment device 2 via the first tapping 52 and the reservoir 24 is filled with water to be treated via the second tapping 54.

[0051] For example, it is possible to list as control members of the treatment device 2 means for adjusting the parameters of its operation such as the valves and pumps described above or additional ones, sensors for measuring parameters such as conductivity or water pressure, etc.

[0052] Advantageously, the treatment device 2 may comprise means for regulating an inlet speed of concentrate and / or water to be treated in the tank 24. For example, these means may allow an inlet of concentrate and / or the water to be treated in the tank 24 at a speed between 0.04 and 0.5 m / s. This speed range is particularly advantageous because it is not too high, as this would generate significant turbulent velocity fields at the time of entry of concentrate or water to be treated into the tank, but high enough to obtain a more clear replacement of the water to be treated by the concentrate and vice versa (too slow a diffusion could lead to a non-negligible local mixing rate).

[0053] The means for regulating an inlet speed of concentrate and / or water to be treated in the tank 24 can be passive (it is for example possible to adjust the diameter of the different conduits connected to the tank 24 in addition to the configuration of the different pumps sending a liquid to the tank 24) and / or active (use of a pressure and / or flow regulator).

[0054] It should also be noted that the hydraulic member(s) 40 and 41 can, depending on their action (for example if it is a perforated plate as described below), also regulate the speed of entry of a liquid into the reservoir 24, or the speed of circulation of this liquid after passing through the latter.

[0055] [Fig.4] illustrates a second embodiment of the invention. Only the differences with the first embodiment are described below.

[0056] In this second embodiment of the invention, the treatment device 2 comprises several reservoirs 24 fluidly connected in series with each other. More precisely, and in this example, these are several external casings of pressure tubes connected in series. Each of the reservoirs 24 corresponds to the definition of a reservoir 24 of the first embodiment by comprising a first hydraulic member 40 and a second hydraulic member 41 fulfilling the aforementioned functions.

[0057] Each tank 24 comprises a first end connected to the tank 24 preceding it in a direction of circulation of the concentrate or the water to be treated (or with a conduit if it is the first or last tank 24), and a second end connected to the tank 24 succeeding it in the direction of circulation of the concentrate or the water to be treated. The connection between the tanks 24 extends substantially perpendicular to their main extension directions A so as to form an elbow between two adjacent tanks 24. This makes it possible to reduce the footprint of the set of tanks 24. The connection point between two adjacent tanks 24 as well as the direction of extension of the connection between them could be different from the example illustrated. It is for example possible to align the tanks 24 in the same direction, preferably parallel to their respective main extension directions.

[0058] Alternatively, the different reservoirs 24 could be connected in series but extend in directions parallel to each other, each reservoir 24 comprising a first tapping fluidly connected to the concentrate discharge pipe 26 and a second tapping connected to the pipe sending the water to be treated 32.

[0059] Figures 5 to 8 illustrate several variants of hydraulic members 40 and 41. These variants are illustrated in a case in which the tapping (here the first tapping 52, but it could be the second tapping 54) is made so as to inject the concentrate or the water to be treated in a direction parallel to the main extension direction A of the tank 24. Of course, the hydraulic members could be used with different positions of the first tapping 52 (or the second tapping 54).

[0060] [Fig.5] illustrates a first variant of a hydraulic member formed by a perforated plate 40' extending inside the reservoir 24.

[0061] In this example, the perforated plate 40' extends substantially perpendicular to the main extension direction A of the reservoir 24 and over the entire liquid passage section in the reservoir 24. The extension direction of the perforated plate 40' in the reservoir 24 as well as the percentage of the liquid passage section covered by the perforated plate 40' could be different. The number of perforated plates used could also vary.

[0062] The perforated plate 40' creates a pressure drop when liquid passes through it. The liquid arriving at its level through the entire passage section of the reservoir 24 can only pass through the through-orifices 68 provided in the perforated plate 40'. This results in a liquid exit, at the level of each through-orifice 68, at a high local speed but over small areas, the speeds decreasing fairly quickly (i.e. over a length of a few centimeters). This then results in a liquid exit from the perforated plate at a homogeneous and more linear speed.As explained above, the dimensioning of the through-orifices 68 as well as their number makes it possible, by knowing the speed of entry of liquid into the reservoir 24, to regulate the speed of circulation of the liquid in the reservoir 24, which can correspond to its speed of entry into the reservoir 24 depending on the placement of the perforated plate (for example against the first opening or the second opening), to obtain a desired speed. Finally, and depending on the dimensions of the perforated plate 40', the incoming liquid can also be distributed homogeneously at the outlet of the perforated plate 40'.

[0063] [Fig.6] illustrates a second variant of a hydraulic member formed by a perforated pipe 40” extending into the reservoir 24 from the first opening delimited by the first tapping 52 (or from the second opening delimited by the second tapping 54).

[0064] The operating principle is similar to that of the 40' perforated plate, the 40” perforated pipe (liquid passing through the perforated pipe only through orifices through-holes 68 provided in the wall of the latter). The difference lies in the positioning of the hydraulic component: the perforated pipe 40” extends directly from the first opening delimited by the first tapping 52 (or from the second opening delimited by the second tapping 54).

[0065] In the example illustrated, the perforated pipe 40” extends substantially parallel to the main extension direction A of the reservoir 24 and comprises through orifices 68 whose positioning leads to injections of liquid into the reservoir 24 in directions perpendicular and parallel to the main extension direction A of the reservoir 24. Of course, and depending on the desired result, at least one of these two parameters could be different.

[0066] [Fig.7] illustrates a third variant of a hydraulic member formed by rectifying plates 40'” of the flow velocity field lines of concentrate and / or water to be treated extending in directions parallel to the main extension direction A of the tank 24.

[0067] The straightening plates 40''' are preferably solid.

[0068] In the example illustrated, a support structure 43 extending into the reservoir 24 and over the entire liquid passage section carries several straightening plates 40'” so as to create several liquid passage sections isolated from each other.

[0069] The shape taken by the straightening plates 40' ' ' could be different from that illustrated in [Fig.7].

[0070] Finally, [Fig. 8] illustrates a fourth variant embodiment in which the first tapping 52 (and / or the second tapping 54) is arranged in the reservoir 24 so as to inject the concentrate and / or the water to be treated in a direction perpendicular to the main extension direction A of the reservoir 24, at least one hydraulic member being arranged so as to straighten a flow of concentrate or water to be treated entering the reservoir 24.

[0071] In the example illustrated, the hydraulic member is formed by the perforated plate 40' extending inside the reservoir 24. Of course, it could be the hydraulic members of the second and third variants.

[0072] Generally speaking, any type of jet breaker can be considered as a hydraulic organ.

[0073] The different valves of the treatment device 2 lead, as explained above, to isolating different compartments of the latter, which leads to the existence of different, or even very different, pressures between different compartments.

[0074] For example, and during the recirculation of the concentrate for extraction of permeate, it is possible that the pressure upstream of the second valve 28 is very high, for example 60 bars, while the pressure downstream of the latter may be equal to the atmospheric pressure. To avoid a shock at the time of opening, it is possible to put in place a bypass around the second valve 28, this bypass comprising a valve smaller than the second valve 28. This valve can be opened a few seconds before the second valve 28 so as to balance the pressures on either side of the second valve 28 so that the opening of the latter (at the same time as an opening of the fourth valve 34 to send water to be treated stored in the tank 24 to the first pressure tube 4), at the time when the concentrate is sent to the tank 24, does not lead to a shock.

[0075] A bypass of the same type can be placed around the third valve 30 for activation at the time of replacement of the concentrate stored in the tank 24 with water to be treated. To do this, the isolation valve 42 is opened and the recharging pump 36 is activated to return water to be treated to the tank 24. The third valve 30 must be open to allow the extraction of the concentrate from the treatment device 2. Here again, the pressure upstream of the third valve 30 can be very high, for example 60 bars, while the pressure downstream of the latter can be equal to atmospheric pressure. A bypass can here again be arranged on either side of the third valve 30, like that which can be placed around the second valve 28, in order to rebalance the pressures on either side of the third valve 30.

[0076] We will now describe the processing method 56 resulting from the implementation of a processing device according to the invention with the support of figures 1 to 3 illustrating the operation of the method according to the first embodiment of the invention.

[0077] [Fig.l] illustrates the treatment device during a recirculation step 58 of the concentrate.

[0078] During this step, the water to be treated is recirculated several times in the recirculation loop 20 by means of the recirculation pump 18, as illustrated by the directional arrows 44 present in [Fig.l]. More precisely, it is raw water during the first pass then increasingly concentrated concentrate during the successive passes. The first valve 22 is open to allow the concentrate to pass through the recirculation loop 20, and the second valve 28 is closed to prevent the concentrate from escaping from the recirculation loop 20.

[0079] At each passage through the reverse osmosis membrane unit and more precisely the desalination modules 6, the permeate is extracted from the water to be treated and is extracted from the treatment device 2 (directional arrow 44 on the arrow 3). The concentrate itself becomes more and more concentrated in salt. There is therefore a progressive increase in the salinity of the concentrate, which requires a progressive increase in the pressure in the main loop, an increase ensured by the pressurization member 14. There is also a loss of water volume linked to the production of permeate which is extracted from the recirculation loop 20 through the desalination module(s). In order to compensate for the loss of volume linked to the production of permeate, the feed pump 10 can provide a flow rate of seawater to be treated identical to the flow rate of permeate by ensuring the necessary increase in pressure (with a possible supplement from the pump acting as a pressurization member 14) in order to maintain constant permeate production.

[0080] Once the maximum salt concentration has been reached (or after reaching a predefined conversion rate or a predefined time), the second step (i.e. the purge step 60) of the process is initiated. This step is illustrated in [Fig.2].

[0081] Once the maximum recovery rate of the cycle has been reached (determined by pressure, conductivity, volume or time), that is to say once it is deemed that it is no longer relevant to circulate the concentrate again in the recirculation loop 20, the concentrate must be evacuated before restarting a new treatment cycle. For this, the recirculation loop 20 is closed (for example by closing the first valve 22, the third valve 30 remaining closed to prevent any exit of the concentrate from the treatment device 2) and the concentrate directed towards the concentrate discharge conduit 26 towards the tank 24, from the concentrate outlet conduit 16 of the first pressure tube 4 (for example by opening the second valve 28).

[0082] The conduit 26 makes it possible to direct the concentrate towards the reservoir 24, more particularly towards the first tapping 46, in which water to be treated is stored, preferably pressurized water. When the concentrate reaches the reservoir 24, it pushes the water to be treated from below into the sending conduit 32 and through the second tapping 48. The fourth valve 34 is opened to allow this. The water to be treated extracted from the reservoir 24 therefore replaces the concentrate in the recirculation loop 20, while the latter is now stored in the reservoir 24. The system is therefore both purged (of concentrate) and filled (with fresh water to be treated) in order to reduce this purge time and thus minimize the loss of production. In parallel, water to be treated from the feed pump 10 can also be injected into the treatment device 2 for the reasons mentioned above.

[0083] The structure of the treatment device 2 according to the invention makes it possible, as explained previously, to limit the concentrate / sea water mixture, which makes it possible to limit as much as possible the contribution of salt in the water to be treated replacing the concentrate in the recirculation loop 20, and thus to limit the water pressure to be applied during the first passage of the water to be treated in the reverse osmosis membrane unit while maximizing the number of passages of the water through the latter.

[0084] A recharging step 62 of the reservoir 24 follows the purging step 60 above. This step can be carried out in parallel with a permeate extraction such as as described above. In fact, the second and fourth valves 28 and 34 are closed while the first valve 22 is open, which makes it possible to isolate the recirculation loop 20. In parallel with this, the third valve 30 is open, as is the isolation valve 42, and the recharging pump 36 supplies the recharging pipe 32' of the tank 24 with water to be treated.

[0085] Water to be treated replaces the concentrate in the tank 24, with possible pressurization of the water stored in the tank 24. The invention also makes it possible, during this replacement, to limit a mixture of sea water and concentrate. Opening the third valve 30 makes it possible to extract the concentrate from the treatment device 2 by passing the concentrate through the first tapping 52 and the conduit 26' for extracting the concentrate from the tank 24. The tank 24 therefore again comprises water to be treated, entered through the second tapping 54, ready to replace a concentrate that is too concentrated in salt during a subsequent purging step.

[0086] The method according to the invention may further comprise steps of regulating the rate of entry of the concentrate and / or the water to be treated into the tank 24.

[0087] The invention is not limited to the embodiments presented and other embodiments will become clear to those skilled in the art. It is in particular possible to provide a conduit architecture different from that shown in the figures, with interdependent or fully separate conduits. It is also possible to provide a set of pumps making it possible to obtain the liquid movements described above. List of references

[0088] 2: processing device

[0089] 3: permeate extraction

[0090] 4: first pressure tube

[0091] 6: desalination module

[0092] 8: water supply pipe to be treated

[0093] 10: feed pump

[0094] 12: first filter

[0095] 14: pressurization organ

[0096] 16: outlet pipe for a concentrate from the reverse osmosis membrane unit

[0097] 18: recirculation pump

[0098] 20: recirculation loop

[0099] 22: first valve

[0100] 24: reservoirs

[0101] 26: Concentrate discharge pipe to the tank

[0102] 26': conduit for extracting the concentrate from the tank

[0103] 28: second valve

[0104] 30: third valve

[0105] 32: pipe for sending water to be treated from the tank to the water supply pipe to be treated

[0106] 32': pipe for recharging the tank with water to be treated

[0107] 34: fourth valve

[0108] 36: refill pump

[0109] 38: second filter

[0110] 40, 41: hydraulic organ [YES] 40': perforated plate

[0112] 40”: perforated pipe

[0113] 40”': straightening plates

[0114] 42: isolation valve

[0115] 43: support structure

[0116] 44: directional arrows

[0117] 46: first wall

[0118] 48: second wall

[0119] 50: side wall

[0120] 52: first stitching

[0121] 54: second stitching

[0122] 56: treatment method

[0123] 58: recirculation step

[0124] 60: purge step

[0125] 62: reloading step

[0126] 64: regulation step

[0127] 68: through holes

[0128] A: main extension direction

Claims

1. Claims Device (2) for treating water to be treated by closed-circuit reverse osmosis comprising: - a reverse osmosis membrane unit configured to produce a permeate and a concentrate from the water to be treated, - at least one conduit for supplying the water to be treated (8) to the reverse osmosis membrane unit, - at least one outlet conduit (16) for the concentrate from the reverse osmosis membrane unit, - at least one conduit forming a recirculation loop (20) and connecting the supply conduit for the water to be treated (8) and the outlet conduit (16) of a concentrate from the reverse osmosis membrane unit so as to allow a return of the concentrate to the reverse osmosis membrane unit, - at least one reservoir (24) delimiting a storage volume, - at least one evacuation conduit (26) for the concentrate towards the tank (24), from the outlet conduit (16) for the concentrate of the reverse osmosis unit, and at least one extraction conduit (26') for the concentrate from the tank (24), - at least one sending conduit (32) for water to be treated stored in the tank (24) to the supply pipe for the water to be treated (8) and at least one refill pipe (32') of the tank (24) with water to be treated, characterized in that the tank (24) comprises a first tapping (52) arranged so as to allow an injection of concentrate into the tank (24) and a second tapping (54) arranged so as to allow an injection of water to be treated into the tank (24), the tank (24) comprising at least one first hydraulic member (40) configured to straighten velocity field lines of a concentrate flow in the tank (24) so ​​as to make them substantially parallel to each other and parallel to a main direction of extension (A) of the tank (24), and at least a second hydraulic member (41) configured to straighten velocity field lines of a flow of water to be treated in the tank (24) so ​​as to make them substantially parallel to each other and parallel to the main extension direction (A) of the tank (24).

2. Treatment device (2) according to claim 1, in which at least one of the first and second hydraulic members (40, 41) extends at a distance of between 0 cm and 25 cm respectively from a first opening delimited by the first tapping (52) or from a second opening delimited by the second tapping (54).

3. A treatment device (2) according to any preceding claim, wherein at least one of the first and second hydraulic members comprises a perforated plate (40') extending inside the reservoir (24).

4. Treatment device (2) according to any one of the preceding claims, in which at least one of the first and second hydraulic members comprises a perforated pipe (40”) extending into the reservoir (24) from a first opening delimited by the first tapping (52) or from a second opening delimited by the second tapping (54).

5. Treatment device (2) according to any one of the preceding claims, in which at least one of the first and second hydraulic members (40, 41) extends substantially perpendicular to a main extension direction (A) of the reservoir (24).

6. Treatment device (2) according to any one of the preceding claims, in which at least one of the first and second hydraulic members (40, 41) extends over at least 50% of a passage section of the reservoir (24).

7. Treatment device (2) according to any one of the preceding claims, in which the first tapping (52) and / or the second tapping (54) are provided in the reservoir (24) so ​​as to inject the concentrate and / or the water to be treated in a direction parallel to the main extension direction (A) of the reservoir (24).

8. Treatment device (2) according to any one of the preceding claims, in which at least one of the first and second hydraulic members is formed of a plurality of straightening plates (40”) of the velocity field lines of flow of concentrate and / or water to be treated extending in directions parallel to the main direction of extension (A) of the tank (24).

9. Treatment device (2) according to any one of the preceding claims, comprising several reservoirs 24 fluidically connected in series with each other.

10. Treatment device (2) according to the preceding claim, in which each reservoir (24) is formed by an external casing of a pressure tube.

11. Treatment device (2) according to any one of the preceding claims, comprising means for regulating an entry speed of the concentrate and / or the water to be treated into the tank (24).

12. A method of treating (56) water to be treated using a treatment device (2) according to any one of the preceding claims, the treatment method (56) comprising repeating, at least once, the following steps: - a recirculation step (58) in which the water to be treated circulates several times in the reverse osmosis membrane unit by passing through the recirculation loop (20), - a purging step (60) in which the concentrate is brought to the tank (24) by the first tapping (52) and water to be treated stored in the tank (24) is sent to the supply pipe for the water to be treated by the second tapping (54), and - a recharging step (62) in which the concentrate is evacuated from the treatment device (2) by the first tapping (52) and the tank (24) is filled with water to be treated by the second tapping (54).

13. Treatment method (56) according to the preceding claim, comprising a step of regulating (64) the rate of entry of the concentrate and / or the water to be treated into the tank (24).

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