WO2009019342A2 - Autonomous device for the purification of sea water having alternating submerged filtration modules having low-pressure chambers connected together - Google Patents

Abstract

The invention relates to a sea water purification device comprising at least one pair of sea water filtration modules (10a, 10b), especially for filtration by reverse osmosis, which are submerged in the marine environment and connected together by a motorized transmission (12, 13, 19) designed to move the filtration modules (10a, 10b) of each pair in reciprocating dipping/raising movements in the marine environment. Each filtration module (10a, 10b) comprises at least one high-pressure chamber associated with at least one low-pressure chamber. The low-pressure chambers of the filtration module (10a, 10b) of a given pair are connected together via at least one duct (69) for balancing the pressures in these low-pressure chambers.

Description

DEVICE SELF-TREATMENT ¹ OF SEA WATER MODULES

OF ALTERNATIVE SUBMERSIBLE FILTRATION WITH LOW ROOMS

PRESS RELATED BETWEEN

The invention relates to a device for purifying seawater comprising at least one pair of seawater filtration modules, in particular by reverse osmosis, immersed in the marine environment and connected to one another by a motorized transmission adapted to move the filtration modules of each pair according to alternating dive and ascending movements in the marine environment in opposition to the phase, each filtration module comprising:

- a chamber, called high pressure chamber, equipped with:

at least one selective inlet (in certain operating phases) in seawater to be filtered at. inside the high-pressure chamber, at least one semi-permeable membrane for filtering seawater by reverse osmosis,

at least one outlet for collecting the filtered water produced by each membrane contained in the high pressure chamber,

at least one outlet of the seawater of greater salinity, a piston face, called the pressurization face, arranged to have a useful area s, and able to move in the high pressure chamber so as to determine the pressure of the seawater at the entrance of each membrane,

a piston face, called a receiving face, arranged to be subjected to the hydrostatic pressure of the marine environment with a useful area of value greater than the useful area of the pressurization face, said receiving face being integral in translation with said face of pressurization, and associated with a sealed chamber in a gaseous atmosphere, said low pressure chamber, so that the volume of this low pressure chamber varies in the same direction as that of the high pressure chamber under the effect of the movements of the face of pressurization. Many devices have been proposed for seawater purification by reverse osmosis for producing fresh water by desalination of inertial water. FR 2503129 describes the principle of a seawater purification device as mentioned above comprising reverse osmosis filtration modules and equipped with a hydrostatic pressure booster system. When a filtration module is lowered to a sufficient depth, the receiving face subjected to the hydrostatic pressure causes a decrease in the volume of the low pressure chamber and a displacement of the pressurizing face in the high pressure chamber so as to reduce its pressure. volume, thus applying a high inlet pressure allowing the operation of reverse osmosis filtration membranes. Such a device makes it possible to obtain a sufficient pressure (which must be at least 50 hPa, ideally 60 hPa) for feeding the membranes in seawater, for a maximum depth of diving of the modules limited to a reasonable value, theoretically of the order of 10 to 30 m. However, to ensure the correct operation of the filtration modules, it is necessary to provide return means, during the recovery of the filtration module to the surface of the marine environment, the pressurizing face, the receiving face and the low pressure chamber in the initial position of maximum volume of the high pressure chamber. However, these return means, as well as the pressure of the gaseous atmosphere that increases in the low pressure chamber as the volume of the high pressure chamber decreases, affect the value of the pressure applied in the high pressure chamber and therefore limit, for a given maximum immersion depth, the amount of filtered water supplied to each dive. These return means constituted for example in the form of a compression spring, constitute mechanical parts subject to wear, in particular corrosion, and therefore limit the reliability and the duration of operation of such a device.

The invention therefore aims to overcome these disadvantages by proposing an improved seawater purification device, in particular using the reverse osmosis phenomenon, for the desalination of seawater and whose operation, reliability and duration of operation are improved.

The invention aims more particularly to provide such a seawater purification device with which the maximum depth of immersion of the filtration modules can be limited to a value between 10 m and 30 m, and with which the quantity Filtered water supplied at each dive is optimized.

The invention aims more particularly to provide such a device free of mechanical return piece or any return member.

The invention also aims to provide such a seawater purification device that is simple and inexpensive in manufacturing and maintenance.

(Throughout the text, the term "motorized" refers generally to any device delivering mechanical energy).

To do this, the invention relates to a seawater purification device comprising at least one pair of seawater filtration modules, in particular by reverse osmosis, immersed in the marine environment and connected to each other. another by a motorized transmission adapted to move the filtration modules of each pair according to alternating dive and rise movements in the marine environment in phase opposition, each filtration module comprising: at least one chamber, said high pressure chamber , equipped with:

at least one selective inlet for seawater to be filtered inside the high pressure chamber,

at least one semi-permeable membrane for filtering seawater by reverse osmosis; at least one outlet for collecting the filtered water produced by each membrane contained in the high pressure chamber;

- at least one outlet of the seawater of greater salinity,

at least one piston face, called the pressurization face, arranged to have a useful area s, and able to move in the upper chamber pressure in order to determine the pressure of the seawater at the inlet of each membrane,

for each pressurizing face, at least one piston face, called the receiving face, arranged to be subjected to the hydrostatic pressure of the marine environment with a total useful area S of value greater than the effective area s of the pressurizing face, each receiving face being integral in translation with said pressurizing face, and associated with at least one sealed chamber in a gaseous atmosphere, called a low pressure chamber, such that the volume of this low pressure chamber varies in the same direction as that of the high pressure chamber under the effect of displacements of the pressurizing face, characterized in that the low pressure chambers of the filtration modules of the same pair are connected to each other by at least one balancing duct of pressures prevailing in these low pressure chambers. Advantageously and according to the invention, each pressure equalization duct is adapted to allow equalization of the pressures between the low pressure chambers substantially without loss of load.

The low pressure chambers of the opposed phase modules are connected, when each low pressure chamber of a filtration module located at depth decreases in volume (during the production of the filtered water) a gaseous atmosphere flow can establish to each low pressure chamber of the filtration module located in the vicinity of the surface of the marine environment, which causes an increase in the volume of this low pressure chamber, and therefore a return of the filtration module in the initial position. In addition, the pressure in each low pressure chamber of the filtration module located at depth does not substantially prevent the displacement of the pressurizing face in the high pressure chamber. The whole is obtained without adding moving parts, and on the contrary makes it possible to overcome any spring or other return member.

Thus, advantageously, a device according to the invention is free of mechanical return member, in particular spring. The invention can be applied to all the embodiments that can be envisaged with regard to the hydrostatic pressure booster means and the reverse osmosis filtration means of each filtration module. It applies in particular to the embodiments described in FR 2503129. This being so, in particular the number and the relative provisions of the high pressure, low pressure chambers, and the pressurizing and receiving faces may vary.

Advantageously and according to the invention, each receiving face is integral in translation with a piston face, called a low-pressure face, extending in a low-pressure chamber. More particularly, advantageously and according to the invention, the receiving face and the low pressure face are two opposite faces of the same piston guided in translation in a sealed manner in a cylinder so as to delimit, with the latter, said low pressure chamber, and in that each pressure equalization duct opens into the low pressure chamber so as to be in communication with this low pressure chamber irrespective of the position of the piston in the cylinder. In addition, advantageously and according to the invention, the pressurization face secured in translation of the receiving face has at least substantially the same orientation as the low pressure face relative to the piston. In particular, advantageously and according to the invention, at least one pressurizing face is connected to at least one low-pressure face by a rod passing through the corresponding low-pressure chamber in a sealed manner. In this advantageous embodiment, said pressurizing face, the receiving face and the low pressure face are faces of the same movable piston formed in one piece or an assembly of several parts integral with each other. Furthermore, advantageously, a device according to the invention is further characterized in that each filtration module is suspended in the marine environment by at least one suspension cable of the motorized transmission, this suspension cable being coupled to a piston delimiting a low pressure chamber. Thus, during the rise of the filtration module, the weight of the latter spontaneously tends to deploy each low pressure chamber in the direction of an increase in its volume, which generates a suction in each low pressure chamber of the other filtration module during descent, via the duct (s) pressure balancing. This aspiration contributes to the training of the pressurizing face and the receiving face of this filtration module during descent.

Furthermore, advantageously, a device according to the invention is further characterized in that the motorized transmission comprises at least one emergent pulley driven in rotation around which is wound at least one suspension cable, one end of which is connected to a module of filtration and the other end is connected to another filtration module, the two filtration modules suspended at the ends of this suspension cable forming a pair of filtration modules moving in opposition of phase and in that each conduit of Pressure balancing extends along such a suspension cable. In an advantageous variant according to the invention, each pressure equalization duct is adapted to act as a suspension cable for the motorized transmission, in particular a suspension cable connecting two filtration modules of the same pair to each other via a cable. deflection pulley emerged. In another variant, a fully submerged pressure equalization duct may be provided for directly connecting the low pressure chambers of the two filtration modules, independently of the suspension and driving mechanism of each filtration module.

Furthermore, preferably, said motorized transmission is adapted to allow movements of each filtration module between the surface of the marine environment and a maximum immersion depth of between 10 m and 30 m, for example of the order of 20 m. . In addition, advantageously and. according to the invention, the ratio of useful areas S / s (for a low pressure chamber comprising 3 pistons) is between 6.6 and 20. Furthermore, advantageously and according to the invention, said motorized transmission comprises at least one renewable energy source selected from a wind turbine and a panel of photovoltaic solar collectors. A wind turbine may be used to directly drive at least one member such as a pulley of a drive mechanism and / or suspension of the two filtration modules of the same pair, with a stop mechanism of displacement and inversion of the direction of movement of each module at the end of the vertical stroke (see for example FR 2503129). As a variant, a wind turbine associated with a current generator and / or at least one panel of photovoltaic sensors supplies at least one battery of electric accumulators adapted to allow the operation of an electric motor for driving at least one organ such as a pulley of a drive mechanism and / or suspension of two filtration modules of the same pair. Stopping the movement and reversing the direction of movement of each module can then result from an electrical automatism changing the direction of rotation of the motor.

It should be noted that when the two filtration modules of the same pair are suspended on the same suspension cable, these two modules being identical and of the same weight, the energy required to drive these two filtration modules in their movements of diving and recovery in the marine environment in opposition of phase is very low.

A device according to the invention may for example be in the form of a fixed platform installed at sea, or in the form of a tower or a well installed on the shore to be filled with seawater.

The invention also relates to a seawater purification device characterized in combination by all or part of the characteristics mentioned above or below.

Other objects, features and advantages of the invention will appear on reading the following description which refers to the appended figures. representative by way of non-limiting examples of the embodiments of the invention, and in which:

FIG. 1 is a general schematic diagram of a first embodiment of a device according to the invention in the form of a maritime platform,

FIG. 2 is a general block diagram of a second embodiment of a device according to the invention in the form of a tower on the maritime shore,

FIG. 3a is a diagram in vertical section of an exemplary embodiment of a filtration module of a device according to the invention, FIGS.

3b and 3c respectively being diagrams similar to FIG. 3a showing this module at the end of the deep dive stroke and, respectively, of the return to the surface,

FIG. 4 is a diagram in vertical section of a second exemplary embodiment of a filtration module of a device according to the invention.

The device according to the invention represented in FIG. 1 comprises a pair of filtration modules 10a, 10b of seawater, in particular by reverse osmosis, immersed in the marine environment 11 and connected to one another by a cable 12 of suspension exiting the water to pass around an emergent pulley 13 mounted in rotation about a horizontal axis 14 on a platform 15 disposed above the surface 16 of the water. The two filtration modules 10a, 10b of the same pair are identical.

The platform 15 is anchored so that it remains at least substantially immobile, as well as the filtration modules 10a, 10b, with respect to the underwater ground 17, and this for example thanks to at least one pole 18 diving in the ground 17, or any other appropriate anchoring system (for example a set of moorings connected to the platform 15 by cables or chains ...). The pulley 13 is coupled to an electric motor 19 which drives it in alternating rotations in one direction and then in the other, under the control of an automaton 35 with stopping phases at the end of a predetermined duration for allow reverse osmosis filtration to take place in the filtration module 10a, 10b immersed at the maximum depth. The controller 35 comprises a man-machine interface (screen, keyboard ...) and is programmable. It can be realized from a standard microcomputer.

The two filtration modules 10a, 10b are connected to each other by the suspension cable 12 and move in phase opposition during the rotation of the pulley 13, one of the filtration modules 10a, 10b being being raised to the surface while the other filtration module 10b, 10a of the same pair is being dipped.

The electric motor 19 is powered by a source of electrical energy, for example a storage battery 20 recharged by a wind turbine 21 coupled to a generator 22 and / or at least one panel of solar photovoltaic collectors 23. The electric motor 19 can incorporating a reduction gear or any other suitable mechanical transmission for driving the pulley 13 at a speed sufficient for the dive and ascent phases to be as rapid as possible, but not too great to avoid any reduction in tension in the cable 12 ( the driving speed of the suspension cable 12 remaining below the maximum diving speed of each module 10a, 10b by gravity).

The platform 15 also carries a tank 24 for recovering the fresh water produced by each of the modules 10a, 10b, all the various components carried by the platform 15, with the exception of the turbine 21 and solar collectors 23, may be protected by a cowling or a building 36. Alternatively, this tank 24 may be located on the mainland especially if the platform 15 is close to the coast.

FIG. 2 represents an alternative embodiment of such a device according to the invention in which the modules 10a, 10b are immersed in a column of seawater 25 located in a tower 26 disposed near the shore. The top 27 of the tower forms a platform similar to the platform 15 of the first embodiment and receiving the same elements 13 to 23 described above. In another variant not shown, the water column may be located in a well dug in the soil of the shore.

The advantage of these two variants with respect to the embodiment of FIG. 1 consists in the fact that the filtration modules 10a, 10b are no longer subjected to the natural environment, and in particular to the marine currents, so that the operation of the device can be more stable. The advantage of the first embodiment of FIG. 1, however, is that it has a lower investment cost, and that it is not necessary to provide suction means for the seawater to be treated. nor means for purging concentrated seawater (of greater salinity).

In addition, in the variant of Figure 2, the recovery tank 24 is located at the bottom of the water column 25, so that the recovery of filtered fresh water is by gravity. However, it should be noted that in the first embodiment shown in FIG. 1, the reverse osmosis filtration modules 10a, 10b provide the fresh water with a pressure that is largely sufficient to allow it to rise to the surface. Thus, in a variant not shown, the recovery tank 24 may be formed of a column extending vertically parallel to the tower 26.

The water column 25 is fed with seawater from a pipe 28 and a pump 29 which can be coupled to the electric motor 19. Preferably, in the embodiment shown in FIG. sea water from an intermediate seawater storage basin 30 at the bottom of tower 26, this basin 30 itself being supplied with seawater by the tides and / or by a connected pipe 31 to a pump 34. Furthermore, a drain pipe 32 is advantageously provided opening at the bottom of the column 25 and provided with a valve 33 drain. This emptying pipe 32 opens into the marine environment. When the valve 33 is open, the column 25 can be emptied, for example for cleaning purposes or in order to extract and renew the seawater at the bottom of the column 25, the salinity of which tends to increase as and when measurement of freshwater production. Moreover, in a variant not shown, the feed pump 29 of the column 25 can be replaced by a continuous-running noria driven directly by the wind turbine 21, and the feed pump 34 of the intermediate basin 30 can be omitted if this intermediate basin 30 is located below sea level and is fed by an inclined pipe. This embodiment is particularly simple and allows the exploitation of the invention with implementation of rudimentary mechanical technologies in the most remote regions of the planet. The repair of such a device is extremely easy to achieve with basic means.

Figures 3a, 3b, 3c show an embodiment of a filtration module 10a, 10b.

This filtration module is globally oblong hydrodynamic facilitating its dive and rise in the water. It therefore comprises an elongated generally cylindrical metal or plastic body 40 with a rounded lower end 41 that can be weighted so as to increase the tension on the suspension cable 12.

In the lower part, above the lower end 41, the body 40 defines a high pressure chamber 42 containing at least one membrane 43 reverse osmosis filtration. In the example shown, the high pressure chamber 42 contains two membranes 43. Each high-pressure membrane 43 has a lower end 44 through which the fresh water filtered by said membrane 43 flows, this end 44 being connected to a pipe 45 The outlet pipe 45 is connected outside the body 40 to a hose 46 for collecting the filtered water, this pipe 46 being itself connected to the tank 24 for collecting the filtered water. water. The high pressure chamber 42 is surmounted by a low pressure cylinder block 47 comprising a plurality of low pressure chambers 48 in series.

The cylinder block 47 is formed of a plurality of cylinder sections 49 of hollow vertical axis stacked on each other axially and separated in pairs by a separating flask 50. Each flange 50 is formed of a disk having a double threading allowing on each side the attachment of a cylinder section 49 whose axial end is provided with a corresponding thread, so as to allow the stacking of the sections. 49 to form a vertical axis cylinder. Each cylinder section 49 contains a piston 51 guided in vertical axial translation in this cylinder section 49.

Each low pressure chamber 48 is delimited between one of the fixed flanges 50 and the piston 51 guided in vertical axial translation in one of the cylinder sections 49 sealingly.

Each piston 51 is generally disk-shaped and has a first main face, called low-pressure face 52, delimiting the low-pressure chamber 48, and a second opposite main face, said receiving face 53, forming with the portion of the cylinder section 49 extending above this receiving face 53 and, where appropriate, with the separating flange 50 located immediately above, a chamber, said receiving chamber 54, subjected to the hydrostatic pressure of the marine environment.

Each cylinder section 49 is provided, at its upper end, with orifices 55 passing through the wall of the cylinder section 49 to allow the free passage of the seawater substantially without loss of pressure from outside (surrounding marine environment) in the receiving chamber 54, so that this receiving chamber 54 and the receiving face 53 are subjected to the hydrostatic pressure of the surrounding marine environment.

The various pistons 51 are integrally connected in vertical axial translation on the one hand to each other by connecting rods 57 and on the other hand to a pressurizing piston 56 penetrating into the high pressure chamber 42. Each connecting rod 57 connects two adjacent pistons 51 to each other by axially sealingly passing through the flange 50 which separates these two pistons 51. To this end, each separating flange 50 is provided with a central axial bore crossing. Each piston 51 may be provided with a double tapping, that is to say a tapping on each of its faces 52, 53 to receive the threaded end of such a rod 57.

The seal between each piston 51 and the inner wall of the corresponding cylinder section 49 is provided by a seal 58 disposed in a central peripheral groove of the piston 51. The seal between each connecting rod 57 and the flange 50 it passes through is also provided by a seal 60 disposed in a central groove opening into the axial through bore formed through the flange 50 for the passage of the connecting rod 57.

The first, lowest cylinder section 49 extends from a flange 63 of the body 40 delimiting the high pressure chamber 42 in the upper part. The first low pressure chamber 48 which is the lowest is therefore delimited between the portion the upper face 64 of the flange 63 extending facing the inside of the first cylinder section 49, and the low pressure side 52 of the first piston 51 which is the lowest.

The pressurizing piston 56 is formed of a rod axially passing through the upper flange 63 of the high pressure chamber 42 in a sealed manner via a central bore formed through this flange 63. This pressurizing piston 56 is connected to said first piston 51 of the side of its low pressure side 52, so as to be integral in axial translation of the latter and the different pistons 51. To do this, the upper end of the pressurizing piston 56 is threaded so as to be screwed into the thread of the low-pressure face 52, in the manner of a connecting rod 57. The opposite free end 78 of the rod forming the pressurizing piston 56 constitutes a pressurizing face 80 moving in the high pressure chamber 42. Thus, the pressurizing piston 56 is connected to each piston 51 so that the pressurizing face 80 of this pressurizing piston 56 is oriented on the same side as the low pressure side 52 of each piston 51, namely horizontally downwards in the embodiment shown.

The pressurizing piston 56 passes through the flange 63 sealingly through a seal 66 disposed in a peripheral groove opening into the central bore formed through the flange 63.

The last piston 51 disposed at the upper end of the cylinder block 47 is suspended from the suspension cable 12. The filtration module 10a, 10b is thus suspended from this suspension cable 12 in the marine environment, with the longitudinal axis of translation of the pressurizing piston 56 which extends vertically. Each low pressure chamber 48 is filled with a gaseous mixture, for example atmospheric air. The wall of each cylinder section 49 is provided in the lower part, immediately above the separating flange 50 on which said cylinder section 49 is assembled, with at least one through orifice 68 communicating with a conduit 69 for balancing the pressures that extend outside the cylinder block 47. This orifice 68 thus allows the free circulation in the conduit 69 for balancing the pressures, the gas contained in the low pressure chamber 48. All the orifices 68 communicating with the different chambers low pressure 48 are connected to the same conduit 69 for balancing pressures. Furthermore, each orifice 68 is disposed in the corresponding low pressure chamber 48 so as to be in communication with this chamber 48 regardless of the position of the piston 51 in the cylinder section 49. In the example shown, the orifice 68 is placed immediately above the separation flange 50, that is to say at the lower end of the cylinder section 49.

The pressure equalization duct 69 is a flexible hose that can be passed along the suspension cable 12, and which connects the two filtration modules 10a, 10b, so that the different low pressure chambers 48 of these two modules of 10a, 10b are in communication with each other, at least substantially at the same gas pressure prevailing inside these different low pressure chambers 48. The number and diameter of the orifices 68, as well as the internal diameter of the conduit 69 for balancing the pressures are indeed adapted to allow the balancing of the pressures between the different low pressure chambers 48, substantially without loss of load. In the variants represented in FIGS. 1 and 2, the pressure equalization duct 69 extends along the suspension cable 12, and passes therethrough around the pulley 13. To do this, this pulley 13 comprises a first throat internal receiving the cable 12, and a second outer groove of greater width receiving the conduit 69.

The outer diameter D1 of the body 40 in its portion delimiting the high pressure chamber 42 corresponds to the overall diameter of the filtration module and is greater than the outer diameter D2 of the low pressure cylinder block 47. In this way, the upper flange 63 has, outside the cylinder block 47, seawater inlets 70 communicating with the interior of the high pressure chamber 42. Each inlet 70 of seawater therefore allows connect the surrounding marine medium inside the high pressure chamber 42, and is sealed by an upper valve 71. Similarly, the lower end 41 of the body 40 is provided with outlets 72 of seawater from greater salinity also communicating with the interior of the high pressure chamber 42. Each outlet 72 of seawater thus makes it possible to connect the surrounding marine medium inside the high pressure chamber 42, and is sealed by A lower valve 73. The various lower valves 71, 73 are integral with each other and carried by a mobile assembly 74 extending inside the high pressure chamber 42 and having a lower horizontal flange 75 and a horizontal flange. upper zontal 76, the latter having a central bore 77 traversed by the pressurizing piston 56. The mobile assembly 74 is adapted so that the lower free end 78 of the pressurizing piston 56 comes into contact with the lower flange 75 at the end of the race downward movement inside the high pressure chamber 42, so as to push the flange 75 down and move the different flaps 71, 73 downward, whereby the seawater inlets 70 and the seawater outlets 72 are open (Figure 3b).

The moving element 74 is also adapted so that a collar 79 integral with the pressurizing piston 56 comes into contact with the upper flange 76 at the end of the upward displacement stroke inside the high pressure chamber 42, so as to pushing the flange 76 upwards and moving the various valves 71, 73 upwards, whereby the seawater inlets 70 and the outlets 72 of seawater are closed (Figure 3c).

As a result, the pressurizing piston 56 controls the opening and closing of the inlets 70 and outlets 72 of seawater.

The different receiving faces 53 of the different pistons 51 have a total useful area S subjected to the hydrostatic pressure of the surrounding marine environment. This total useful area S is equal to the sum of the useful areas S1, S2,..., Sn of each receiving face 53. The pressurizing face 80 of the pressurization piston 56 has a useful area corresponding to the area of the section of the rod forming this pressurizing piston 56.

The total effective area S of the different receiving faces 53 (that is to say the sum of the areas Si of each receiving face 53 receiving the hydrostatic pressure of the surrounding marine environment) is greater than the useful area s of the pressurizing piston. 56 and the ratio of useful areas S / s is advantageously between 6.6 and 20, in particular of the order of 10 and Si / s is advantageously between 20 and 60, in particular of the order of 30.

The hydrostatic pressure experienced by the different receiving faces 53 is transmitted, with an amplification ratio corresponding to the ratio of the useful areas S / s, to the high pressure chamber 42. When the filtration module 10a, 10b is in a dive and goes down in the marine environment, the hydrostatic pressure increases, as well as the pressure in the high pressure chamber 42. When the filtration module 10a, 10b is immersed to a sufficient depth, the pressurizing piston 56 thus prints in the high pressure chamber 42 a pressure of sufficient value (typically greater than or equal to 60 hPa) to allow filtration by reverse osmosis by the membranes 43. The volume of each low-pressure chamber 48 varies in the same direction as that of the high-pressure chamber 42 under the effect of displacements of the pressurizing piston 56. Thus, when the pressurizing piston 56 of a pressurization module 56 filtration 10a, 10b immersed at the maximum depth moves downwardly into the high pressure chamber 42, the volume of the different low pressure chambers 48 decreases. In doing so, the pressure equalizing duct 69 transmits a corresponding increase in pressure to the low pressure chambers 48 of the other filtration module 10b, 10a which is then close to the surface (at the end of the upstroke). In this way, the low pressure chambers 48 of this other filtration module 10b, 10a increase in volume, under the effect of this pressurization via the pressure equalization duct 69, which automatically recalls the pressurizing piston 56 in position high.

FIG. 3a shows the filtration module 10a, 10b while it is at the maximum diving depth, during the displacement of the pressurizing piston 56 downwards, filtered fresh water being produced at the exit of the membranes 43.

Figure 3b shows the filtration module 10a, 10b at the beginning of ascent. In this position, the pressurizing piston 56 has reached the end of its downward movement path inside the high pressure chamber 42, until it comes into contact with the lower flange 75 by moving the moving assembly 74 towards the bottom to open the inlets 70 and the outlets 72. In this way, during the ascent, the seawater passes through the high pressure chamber 42 while sweeping the membranes 43. This sweeping effect is conducive to the functioning of the membranes by reverse osmosis 43. Furthermore, during this ascent, the filtration module 10a, 10b being suspended by the last piston 51, the entire weight of the filtration module 10a, 10b tends to cause the volume increase of the low pressure chambers 48. In addition, as indicated above, this increase in volume is also caused by the pressure increase in the low pressure chambers 48 resulting from the diving of the filtration module 10b, 10a complementary to the same pair connected to the other end of the cable 12 and the other end of the conduit 69 for balancing pressures.

FIG. 3c shows the filtration module 10a, 10b at the end of the ascent (in the vicinity of the surface of the marine medium), the pressurization piston 56 being at the end of the upward displacement stroke and having pushed back the upper flange 76 and therefore the mobile assembly 74 upwards until the valves 71, 73 close the inlets 70 and, respectively, the outlets 72 of seawater. The low pressure chambers 48 have their maximum volume. The high pressure chamber 42 is filled with seawater ready to be filtered by the membranes 43. The filtration module 10a, 10b is ready to perform a new dive.

FIG. 4 shows an alternative embodiment of a filtration module 10a, 10b in which the pressure equalization duct 69 acts as a suspension cable for each filtration module 10a, 10b. In addition, this duct 69 is directly connected to the first piston 51 by a sealing connection 85. Each of the connecting rods 57 is formed of a hollow tube, and each piston 51 is provided with a central through passage 86, so that the air pressure can flow from the connection 85 through the various connecting rods 57 and through the various pistons 51. Each connecting rod 57 also has at least one opening 87 opening in the upper part of this connecting rod 57 in the low-pressure chamber 48. The pressurizing piston 56 is also hollow and in communication with the passages formed in the pistons 51 and in the connecting rods 57. Also, an orifice 88 opens into the upper part of the pressurizing piston 56 into the first low pressure chamber 48 disposed immediately above the flange 63 and the high pressure chamber 42. Thus, the communication between the different low pressure chambers 48 is established via the various orifices 87, 88, the hollow pressurization piston 56, the various hollow connecting rods 57 and the axial passages 86 of the pistons 51, to the conduit 69 pressure balancing. This embodiment is more compact, and furthermore makes it possible to minimize the risk of leakage by the portions of the duct 69 extending, in the first embodiment described above, along and outside the cylinder block 47. .

It should be noted that in the embodiment shown in FIG. 4, the pressurization piston 56 is hollow over its entire length, that is to say is formed of a hollow tube, closed at its lower end 78 by a plug 89 waterproof welded forming the pressurizing face 80. Alternatively not shown, it is possible to use a full cylinder forming the pressurizing piston 56, only an air communication passage in the upper part is provided to connect the pressure equalizing conduit 69 inside the low pressure chamber 48 via the orifice 88 and the central passage of the piston 51 to which the piston 56 of pressurization is connected.

Furthermore, this second embodiment differs from the first in that the length of the piston 55 of pressurization is limited to that strictly necessary, corresponding to the stroke of the pistons 51 of the low pressure cylinder block 47. Thus, the collar 79 is formed at the end 78 of the piston 56 by the plug 89.

For a given maximum depth of diving, the low pressure cylinder block 47 comprising a plurality of pistons 51 and a plurality of low pressure chambers 48 makes it possible to increase by the same the flow rate of filtered water produced at each filtration step (FIG. that is to say at each dive) for a predetermined stroke of the pressurizing piston 56 in the high pressure chamber 42. Indeed, the useful area s of the pressurizing piston 56 can be increased proportionally with the increase of the total effective area S receiving the hydrostatic pressure thus obtained while maintaining the same amplification ratio of pressure. Thus, in a device according to the invention, the amount of filtered water supplied to each dive is optimized.

Or, for a useful area s and a translation stroke given by the pressurizing piston 56, the multiplication of the pistons 51 and the low pressure chambers 48 makes it possible to reduce by as much the maximum diving depth at which the filtration modules 10a, 10b must be placed to perform reverse osmosis filtration. In practice, this maximum immersion depth is advantageously between 10 m and 30 m, and for example is of the order of 20 m. It should be noted that this depth is determined, as a function of the pressure amplification ratio produced by the ratio of the S / s areas, relative to the median receiving face 53, or to the zone situated at the mid-height of the low block. pressure 47.

Furthermore, it should be noted that this improvement in the production of fresh water is obtained without modification of the overall section of the filtration module 10a, 10b, that is to say without modification of its hydrodynamic characteristics. On the contrary, the overall transverse bulk of the filtration module is reduced. In particular, it should be noted that each receiving face 53 has a diameter smaller than the diameter of the high pressure chamber 42.

In practice, in a variant not shown, the overall transverse bulk of the filtration module 10a, 10b may be limited to that which is just necessary to contain a reverse osmosis filtration membrane 43 and the different valves 71, 73 and mobile equipment 74 control these valves. Indeed, this membrane 43 may be disposed at the lower end of the body 40, and the piston 56 can move in an upper axial end portion of the high pressure chamber. The membranes 43 may then be replaced by a single equivalent membrane, of large diameter, occupying the lower axial end portion of the high pressure chamber. In addition, in this variant not shown, the area s of the pressurizing piston 56 may be maximum, and occupy almost the entire cross section of the high pressure chamber 42. The number of the receiving faces 53, the low pressure chambers 48 and the cylinder sections 49 stacked on each other, is determined according to the value of the area S that it is desired to obtain. This number can be between 2 and 60, typically between 3 and 30. For example, if one chooses to perform the filtration module ₅ 1Oa 10b substantially in the form of a minimum transverse cross-section of tube to contain a filtering membrane 43 with a piston 56 of maximum diameter and receiving faces 53 whose diameter also corresponds substantially to that of the piston 56 Si / s = 1, and to obtain a ratio S / s of the order of Si / s = 1, it is necessary to stack thirty receiving faces 53 (for a depth of 20 m).

The filtration module 10a, 10b can be integrated into a casing in generally oblong hydrodynamic shape. For example, in a variant not shown, a filter may be provided around the low pressure cylinder block, in the extension of the housing defining the high pressure chamber. In addition, each filtration module can also be guided in its dive and lift movements, by one or more vertical rails extending into the marine environment. Inside these rails may be arranged crowns of comb-brushes stacked at a distance between them, and intended to rid the filter of the elements (which can become clogging by accumulation) throughout the dives and lifts to to form a self-cleaning system. Nothing prevents also provide a mechanism (not shown) for locking the movement of each pressurizing piston 56 as a minimum hydrostatic pressure is not reached. This mechanism can be of the hydrostatically controlled type. Alternatively, it can be controlled by the controller 35 controlling the operation of the device. Nevertheless, the invention makes it possible to overcome such a mechanism in view of the fact that the filtration modules 10a, 10b have particularly efficient hydrodynamic shapes, increasing their speed of displacement in the marine environment, and therefore decreasing the duration of the dive and ascent phases. Alternatively also not shown, a device for controlling the pressure in the low pressure chambers 48 may be provided, possibly with means for the reintroduction of gas in the low pressure chambers 48 from the surface. For example, the pressure equalization duct 69 may be connected to a duct opening on the surface with a valve that can be opened to inject pressurized air into this duct.

69, at least one low pressure chamber 48, and preferably each of these low pressure chambers 48, being provided with a calibrated valve allowing, during the injection of air under pressure in this low pressure chamber 48, the emptying of the water possibly infiltrated in the low pressure chamber 48.

The device according to the invention can be the subject of many other variants with respect to the embodiments shown in the figures and described above.

In particular, the device according to the invention may comprise several pairs of filtration modules 10a, 10b, connected together or independently of each other. Also, the invention applies to all the embodiments provided in FR 2503129. Each filtration module 10a, 10b may comprise several high pressure chambers, and several pressurizing pistons may be provided for each high pressure chamber. The same low-pressure chamber can receive several low-pressure pistons, that is to say, be associated with several receiving faces, as they move in the same direction of variation of the volume of said low pressure chamber. Conversely, at least one receiving face may be associated with several low pressure chambers. In addition, each high pressure chamber can be associated with several low pressure cylinder blocks 47.

Similarly, the orientation of the different pistons 51, 56 may be different. For example, the various low-pressure pistons are not necessarily parallel to the longitudinal axis of the pressurizing face. Nothing prevents for example to provide low pressure pistons radially movable. But in the latter case, it is necessary to provide a mechanical transmission with a bevel gear to drive the pressurizing face from the displacement of each piston. The number of receiving faces, the number of low pressure chambers, the number of low pressure cylinder (s), the number of pressurizing faces and the number of high pressure chamber (s) of each filtration module may vary. .

The motorized transmission formed by the suspension cable 12, the pulley 13 and the motor 19 can be replaced by any other form of motorized transmission for driving the filter modules 10a, 10b in pairs in opposite phase.

In particular, in an advantageous variant, the engine is formed only of a wind turbine engine as a source of renewable energy. The device is then a desalinating device completely autonomous in its operation, free of means likely to limit its life (electric motor, pump, solenoid valve, electronics ...) and thus having a reliability and a long service life.

Nothing prevents also having a high pressure chamber above a low pressure cylinder block, or even interposed between two low pressure cylinder blocks. The suspension cable 12 may be attached not to one of the pistons 51, but directly to the body 40 of the filtration module 10a, 10b. Also, the pressure equilibrium conduit 69 may be formed of a specific pipe extending integrally under water by connecting the low pressure chambers. The automaton 35 may be replaced by an automatic mechanism for reversing movements, with a mechanical device for controlling the stopping phases of the filtration modules 10a, 10b from a transmission of the movement of the pistons and / or the valves to the inversion mechanism located on the surface.

Of course, the invention also applies to a filtration module comprising a single low pressure chamber 48, as for example described in FR 2503129.

Claims

1 / - A device for purifying seawater comprising at least one pair of filtration modules (10a, 10b) of seawater immersed in the marine environment and connected to each other by a motorized transmission ( 12, 13, 19) adapted to move the filtration modules (10a, 10b) of each pair in alternating dive and upward movements in the marine environment in phase opposition, each filter module comprising: at least one chamber, called high pressure chamber (42), provided with: - at least one inlet (70) for selective admission of sea water to be filtered inside the high pressure chamber (42), ^• at least one semipermeable membrane (43) for filtering seawater by reverse osmosis, at least one outlet (45) for collecting the filtered water produced by each membrane (43) contained in the high-pressure chamber (42); at least one outlet (72) for evacuating the seawater saturated with salinity, at least one piston face, called the pressurizing face (80), arranged to have a useful area s, and able to move in the high pressure chamber (42) so as to determine the pressure of the seawater at the entrance of each membrane (43), - For each pressurizing face (80), at least one piston face, said receiving face (53), arranged to be subjected to the hydrostatic pressure of the marine environment with a total useful area S of greater value than the effective area s of the pressurizing face (80), each receiving face (53) being integral in translation with said pressurizing face (80), and associated with at least one gas-tight chamber, said low-pressure chamber (48), of such so that the volume of this low pressure chamber (48) varies in the same direction as that of the high pressure chamber (42) under the effect of displacements of the pressurizing face (80), characterized in that the low pressure chambers (48) of the filtration modules (10a, 10b) of the same pair are connected to each other by at least one pressure equalization duct (69) low pressure rooms (48). 2 / - Device according to claim 1, characterized in that each duct (69) pressure equalization is adapted to allow equalization of the pressures between the low pressure chambers (48) substantially without loss of load. 3 / - Device according to one of claims 1 or 2, characterized in that each receiving face (53) is integral in translation with a piston face, said low pressure side (52), extending in a low chamber pressure (48). 4 / - Device according to claim 3, characterized in that the receiving face (53) and the low pressure side (52) are two opposite faces of the same piston (51) guided in translation in a sealed manner in a cylinder (49). ) to define, with the latter, said low pressure chamber (48), and in that each pressure equalization duct (69) opens into the low pressure chamber (48) so as to be in communication with this chamber low pressure (48) regardless of the position (51) of the piston in the cylinder (49). 5 / - Device according to claim 4, characterized in that the pressurizing face (80) integral in translation with the receiving face (53) has at least substantially the same orientation as the low pressure face (52) relative to the piston ( 51). 6 / - Device according to one of claims 4 or 5, characterized in that each filter module (10a, 10b) is suspended in the marine environment by at least one cable (12) for suspension of the motorized transmission, this cable Suspension member (12) being coupled to a piston (51) defining a low pressure chamber (48). Il - Device according to one of claims 1 to 6, characterized in that the motorized transmission (12, 13, 19) comprises at least one pulley (13) driven in rotation around which is wound at least one suspension cable (12), one end of which is connected to a filtration module (10a, 10b) and the other end of which is connected to another module of filtration (10a, 10b), the two filtration modules (10a, 10b) suspended at the ends of this suspension cable (12) forming a pair of filtration modules (10a, 10b) moving in phase opposition and in that each pressure equalizing duct (69) extends along such a cable (12). suspension. 8 / - Device according to one of claims 1 to 7, characterized in that each conduit (69) for balancing pressures is adapted to be able to act as a cable (12) for suspending the motorized transmission (12, 13, 19). 91 - Device according to one of claims 1 to 8, characterized in that said motorized transmission (12, 13, 19) is adapted to allow movement of each filter module (10a, 10b) between the surface of the marine environment and a maximum immersion depth of between 10 m and 30 m. 10 / - Device according to one of claims 1 to 9, characterized in that the ratio of useful areas S / s is between 6.6 and 20. 11 / - Device according to one of claims 1 to 10, characterized in that said motorized transmission (12, 13, 19) comprises at least one renewable energy source selected from a wind turbine (21) and a solar collector panel photovoltaic (23).