WO2019193056A1 - Device for purifying water, notably salt water, by low-pressure evaporation - Google Patents

Abstract

Device for purifying water (10), notably saltwater, comprising an evaporation chamber (7) comprising an inlet to receive a volume of water that is to be purified and performing a vapour extraction phase, a condensation chamber (8) comprising an outlet for the purified water and performing a vapour recovery phase, characterized in that it comprises a gas transfer device comprising an interface system delimiting mobile partitions (1, 2) between the two chambers, a system of pistons (3, 4) coupled to the interface system to move the mobile partitions (1, 2) on command, a motor crankcase chamber (5) containing a device (6) for setting said system of pistons (3, 4) in motion, all the pistons describing a cyclic path, the pistons (3, 4) being associated in pairs, two pistons of a pair describing the same path in a movement that is offset by half a cycle with respect to one another, such that the motion imparted to the pistons is designed to keep the motor crankcase (5) at a constant volume, the evaporation chamber (7), the motor crankcase chamber (5), the condensation chamber (8) being connected, at least during a transient phase, to one or more vacuum pumps (9a, 9b, 9c) so that, on each piston, the pressure exerted by the motor crankcase chamber (5) is substantially equal to a pressure Po exerted by the evaporation chamber (7).

Description

 DEVICE FOR PURIFYING WATER, ESPECIALLY SINATED WATER, BY LOW-PRESSURE EVAPORATION

GENERAL TECHNICAL FIELD

The present invention relates to a device for purifying water, especially salt water.

 The present invention also relates to a method for purifying water and in particular salt water.

STATE OF THE ART

 Saltwater accounts for 97% of the total water volume on the planet, making it a significant water reservoir compared to only 3% of available freshwater.

 Desalinating seawater can help cope with the water scarcity threatening many countries and their populations

 200 million people are supplied with desalinated water and considerable new needs are likely to emerge in the next 50 years. Power plants also consume water. A slice of plant needs 400 cubic meters of demineralized water daily. This water can come from seawater desalinated.

The two main desalination methods currently used are distillation and reverse osmosis.

Distillation consists of heating the salt water, recovering the vapor and finally condensing this vapor.

Several distillation variants exist, such as, for example, the distillation by successive expansion also called multi-flash and the multi-effect distillation. Successive or multi-flash distillation

 Seawater is introduced into a chamber heated to 120 ° C where there is a low pressure. This results in an instant flash vaporization called flash. A fraction of the water evaporates and then condenses on condenser tubes placed at the top of the enclosure, and the liquid water is collected in receptacles placed below these tubes.

 The fraction of the seawater that has not evaporated passes into a second stage where there is even less pressure and where the phenomenon of product flash again. It is possible to achieve the vaporization of the water and by successive detents in a series of stages where reign pressures increasingly reduced. Up to 40 successive floors can be found in an industrial unit.

Multi-effect distillation

 Seawater is collected and heated to a varying temperature between 70 and 80 ° C.

 A first part of this water is introduced into the first effect, an enclosure where there is a low pressure and having a first heated exchange surface.

 This introduced water comes into contact with the first exchange surface and evaporates.

 This first vapor thus produced goes into a circuit so as to heat the second exchange surface in the second effect, a second chamber where there is even lower pressure.

 A second portion of the seawater taken and heated is introduced into the second effect and evaporates in contact with the second exchange surface.

 There is then on the one hand evaporation of this introduced water, and on the other hand condensation of the first vapor because of the heat of condensation exchanged.

The process can be cascaded over several effects. Only the energy needed for evaporation in the first effect is of external origin, the multiplication of the number of effects making it possible to increase the efficiency of the system.

Desalinization by reverse osmosis

 Osmosis is a natural phenomenon. When a pure water compartment is separated by a membrane from a seawater compartment, the osmosis phenomenon causes some of the pure water through the membrane to the seawater compartment.

 Reverse osmosis desalinization consists in reversing this phenomenon by applying a high pressure, higher than a so-called osmotic pressure, on the seawater compartment.

These different techniques have weak points concerning the energy cost, the use of chemical treatments, the discharge of very salty water, and finally the discharges of hot water.

The energy cost for the distillation whatever its type is important because it is necessary to provide the necessary energy of latent heat of all or part of the desalinated water to evaporate it. The energy cost is of the order of 10kWh per cubic meter of water produced.

 Reverse osmosis at a lower energy cost than distillation, of the order of 4 kWh per cubic meter of water produced, however it requires more chemical treatments.

It may indeed be necessary to use chemical treatments to ensure the proper implementation of these processes.

In the case of reverse osmosis different chemical treatments are needed, such as biocidal treatments to avoid development microorganisms on the membrane, or acid treatments to avoid precipitation of carbonates on the same membrane.

In the case of multi-effect distillation, the boiling of the seawater within each cell is in contact with the heat exchange surface, there is a risk of scaling due to the precipitation of salts such as CaSO4 or CaCO3 whose solubility decreases with increasing temperature. To mitigate these risks, acid treatment must be used.

Problems of the prior art

 In all these techniques, the rejected water is highly concentrated in salt. There is approximately 1 to 4 liters of water discharged per 1 liter of desalinated water produced. At the level of the rejects, this makes a salt concentration of 1, 25 to 2 times higher than the original concentration, which is not environmentally neutral. This in some cases imposes discharges off the coast with the associated costs of such water transport.

Finally, in the case of distillation, part of the water is evaporated, which is accompanied by an increase in the temperature of the waste. There may be environmental impacts, particularly on the survival of ecosystems close to the places of release.

PRESENTATION OF THE INVENTION

 A general object of the invention is to overcome the disadvantages of water purification systems of the state of the art.

 In particular, an object of the invention is to propose a solution for reducing the energy cost of a water purification process.

The object is achieved within the scope of the present invention by means of a device for purifying water, in particular salt water, comprising an evaporation chamber comprising an inlet for receiving a volume of water to be purified and providing a vapor suction phase, a condensation chamber comprising an outlet for the purified water and providing a vapor recovery phase,

an interface system delimiting movable separations between the evaporation chamber and the condensation chamber,

a piston system coupled to the interface system to move them to order,

a engine-cylinder chamber containing a device for moving said piston system, all the pistons describing a cyclic trajectory,

characterized in that the pistons are associated in pairs, two pistons of a pair describing the same trajectory in a movement offset by half a cycle relative to each other, so that the setting in motion of the pistons is adapted to maintain a constant volume of the breech chamber.

The technical solution performed here allows evaporation of the water to be purified by depression in the evaporation chamber.

 This evaporation does not cause an increase in the temperature of the water and there are therefore no disadvantages related to the presence of hot water.

 Moreover, this device does not require the use of chemical treatment. On the one hand moving parts such as movable separations and pistons only come into contact with purified water, they do not require special protection. On the other hand, the part of the evaporation chamber in contact with seawater can be easily protected from the effects of degradation of the water to be purified using materials known from the prior art such as silicone.

Finally, the constant maintenance of the volume of the engine-cylinder chamber makes it possible to maintain and control the pressure exerted on one of the walls of each piston, in particular the wall of the piston situated on the side of the chamber. cylinder engine. In this way, the energy required for the aspiration of the vapors can be controlled and decreased, thus decreasing the economic cost of the purification.

Advantageously, but optionally, the system according to the invention may further comprise at least one of the following characteristics:

 all the pistons describe the same cyclic trajectory, the positions of the pistons being regularly distributed in the cycle of the movement. the evaporation chamber, the engine-cylinder chamber, the condensation chamber are connected, at least during a transient phase, to one or more vacuum pumps so that on each piston, the pressure exerted by the engine-cylinder chamber is substantially equal to a pressure Po exerted by the evaporation chamber. on each piston, the pressure exerted by the engine-engine chamber is greater than the pressure exerted by the condensation chamber.

 the evaporation chamber comprises a thermal contact with a hot source at a temperature To,

the condensation chamber comprises a thermal contact with a cold source at a temperature T _e lower than To.

 the temperature To is between 5 and 50 degrees Celsius, preferably of the order of 27 degrees Celsius.

the pressure Po is between 8 and 123 millibars, preferably of the order of 36 millibars.

These characteristics make it possible to control more finely the pressure exerted on the walls of each piston. If the pressure exerted by the engine-cylinder chamber is equal to the pressure exerted by the evaporation chamber, the energy associated with the displacement of the pistons becomes minimum in the suction phase and essentially contains only the friction contributions, of mass shift work pistons and moving parts associated with the movement of the pistons and finally the work of moving the mass of steam.

The system according to the invention may further comprise at least one of the following features:

 each piston comprises a deformable membrane

 the deformable membrane consists of a layer of elastomer or of any other deformable material, for example polyethylene, preferably LDPE, advantageously with a thickness of between 10 μm and 10 μm.

 the membrane has a square shape

 the membrane has an indeformable central part

 the central portion is reinforced by a metal spider whose ends are housed in polyethylene fingers, preferably LDPE, heat sealed to the membrane.

 the metal spider comprises several branches each consisting of round hollow aluminum.

 the hollow aluminum is of a thickness of between 0.5 and 1.5 millimeters in thickness.

the hollow aluminum rounds have a diameter of between 7 and

9 millimeters.

 the fingers have a thickness of between 70 and 130 μm.

 the zones of the membrane heat-sealed to the polyethylene fingers are reinforced by a LDPE thickness of between 70 and 130 μm.

These features make it possible to reduce the friction of the pistons and the moving parts, the energy corresponding to the work of displacement of the mass of the latter.

LDPE, a material known for its flexibility, is of common use and low cost and has good heat sealability. This choice makes it possible to reduce the economic cost and to obtain particular forms of the membrane.

 A square or circular shape of the membrane with a non-deformable central part makes it possible to move more steam with the same return of the piston.

 In addition, the square shape reduces the size of the system, because it is then possible to install the pistons next to each other by limiting the unused surfaces for the aspiration of vapors.

The subject of the invention is also an assembly comprising:

a cooling circuit of a power plant adapted to use seawater as a coolant comprising a cold fluid inlet path and a hot fluid outlet path,

a device according to a possible combination of the features presented above and adapted so that:

the flow of the cooling fluid through said cooling circuit is at least one hundred times greater than the flow of water purified by said device, the condensation chamber is in thermal contact with a part of the cold inlet way,

the evaporation chamber is in thermal contact with a portion of the hot outlet channel,

one or more ducts connect the evaporation chamber and the hot outlet way so that a portion of the cooling fluid passing through the hot exit channel can be removed and introduced into the evaporation chamber, and a part liquid in the evaporation chamber can be removed and introduced into the hot outlet.

These characteristics make it possible to use the cooling circuit cold channel as the cold source of the condensation chamber and the hot channel of the cooling circuit for maintaining the temperature in the evaporation chamber. Since the flow through the cooling circuit is much greater than the flow of purified water, the two channels of the cooling circuit can be considered as almost infinite sources of heating of the evaporation and cooling chamber of the cooling chamber. condensation.

 In addition, the ducts connecting the evaporation chamber and the hot outlet channel allow fluid exchanges between the two.

 In particular, the very salty water contained in the evaporation chamber when purified vapor has been extracted can be rejected in the hot exit way. Since the flow through the cooling circuit is much greater than the stream of purified water, the variation in salt concentration generated by the liquid discharges in the hot exit channel is very small. This makes it possible to eliminate the release of very salty water at sea.

The invention also relates to a method for purifying water, especially salt water, which uses the devices and the assembly as described in this section.

In particular, the invention relates to a method for purifying water, especially salt water, characterized in that it is implemented by a device as described in this section and comprising the following steps :

 Supply of water to be purified in the evaporation chamber;

 Operation of a hot source to raise the temperature of the evaporation chamber;

Operating a cold source to create a temperature zone T _e in the condensation chamber;

 Evacuation of the air in the evaporation chamber, the condensation chamber and the engine-cylinder chamber to reduce the pressure;

Piston system and coupled interfaces set in motion, according to the following cycle for each piston and coupled interface: o Isolation of the condensation chamber by the interface;

o Suction of the steam from the evaporation chamber by the piston; o Piston evaporation chamber insulation through the interface;

o Recovery of steam in the condensation chamber by pushing the piston;

Condensation of the vapor in the temperature zone T _e in the condensation chamber.

Advantageously, but optionally, the method may further comprise at least one of the following steps

 Evacuation of the air in the evaporation chamber and the engine-cylinder chamber, which reduces the pressure to the same pressure value in these two chambers.

The invention also relates to a method for purifying water, especially salt water, which uses the assembly as described in this section and comprising the following steps:

 supply of water to be purified in the evaporation chamber by

withdrawing a portion of the cooling fluid passing through the hot exit channel;

 stabilizing the temperature of the evaporation chamber at the temperature of the hot exit channel by thermal contact with a portion of the hot exit channel;

 stabilizing the temperature of the condensation chamber at the temperature of the inlet cold way by thermal contact with a part of the cold inlet channel;

evacuation of the air in the evaporation chamber, the condensation chamber and the engine-cylinder chamber to reduce the pressure; actuating the piston system and the coupled interfaces, according to the following cycle for each piston and coupled interface: o Isolation of the condensation chamber by the interface; o Suction of the steam from the evaporation chamber by the piston; o Piston evaporation chamber insulation through the interface;

o Recovery of steam in the condensation chamber by pushing the piston;

 condensation of the steam in the condensation chamber.

Advantageously, but optionally, this water purification process may further comprise a step where a part of the liquid present in the evaporation chamber is removed and introduced into the hot exit channel when the salt concentration of the liquid present in the evaporation chamber exceeds a predetermined threshold.

PRESENTATION OF FIGURES

 The invention will be better understood, thanks to the following description, which refers to a preferred embodiment, given by way of non-limiting example and explained with reference to the attached schematic drawings, in which:

 - Figure 1 is a diagram illustrating a water purification device, including salt water.

 Figure 1a is a diagram illustrating another device for purifying water, especially salt water.

 FIG. 2 is a diagram illustrating a piston which comprises a

deformable membrane.

 FIGS. 3A, 3B are diagrams illustrating a deformable piston which comprises a deformable membrane whose central part is

indeformable, and Figure 3C a diagram of the volume generated by the beat of such a piston.

 FIG. 4 is a diagram illustrating an exemplary structure of

deformable membrane whose central part is indeformable and square. FIG. 5 is a diagram illustrating a set of a circuit of

cooling of a power plant and a water purification device.

 FIGS. 6A, 6B, 6C, 6D, 6E and 6F represent a piston duct in a device for purifying water, in particular salt water.

DETAILED DESCRIPTION

 Principle of the invention

 FIG. 1 is a diagram illustrating a device for purifying water, in particular salt water, comprising a motor-cylinder chamber 5. This chamber contains a device 6 for setting in motion a piston system 3, 4, all pistons describing the same cyclic trajectory.

 In the particular case of Figure 1, each piston 3, 4 describes a vertical path, up and down within a piston pipe 1 January.

The device contains a system of interfaces delimiting movable partitions 1, 2 between two chambers 7, 8.

 The piston system 3, 4 is coupled to the interface system.

 Each piston (3 respectively 4) is associated with a movable separation (1 respectively 2). In the particular case of Figure 1, when a piston rises the associated interface is in the vertical position and when the associated interface descends is in a horizontal position.

 The pistons 3, 4 are pairwise associated, and two pistons of a pair describe a movement offset by half a cycle with respect to each other. In the particular case of Figure 1, when a piston (3 respectively 4) rises by a certain height the other piston (4 respectively 3) descends the exact same height.

In this way the volume variations of the engine-cylinder chamber 5 produced by a piston (3 respectively 4) are compensated by the volume variations produced by the other piston (4 respectively 3). The volume of the breech chamber 5 thus remains constant over time.

According to another exemplary embodiment, the device may contain several pairs of pistons. All the pistons can describe the same cyclic trajectory, two pistons of a pair being shifted in their half-cycle movement with respect to each other. If at any time, the positions of all the pistons are evenly distributed over the entire cycle of the movement, then it is possible to obtain a balanced distribution of the forces exerted on the device 6 of setting in motion a piston system 3, 4. The power to be delivered by the moving device is smoothed over time, and this limits the irregularities and the sudden effects that use the parts more.

The device may also contain a pair of pistons that describe a cyclic path different from the other pistons.

 These two pistons are offset in their half-cycle movement relative to each other, as for the other pairs of piston.

 Overall, the set of pistons thus configured produces the technical effect of compensating the volume variations of the engine-cylinder chamber produced by this pair of pistons.

 The volume of the breech chamber 5 thus remains constant over time.

Concerning the system of interfaces and mobile separations, it is possible to use solenoid valves. The closing / opening times are of the order of a millisecond, which allows operation of 10,000 revolutions per minute, or 166 revolutions per second.

Each piston can be associated with two solenoid valves which control the communication of the piston with the evaporation chamber and the other with the condensation chamber. These solenoid valves can be synchronized to the device 6 for setting the piston system in motion by servocontrol.

 For example an optical sensor can trigger a solenoid valve depending on the movement of a part that drives one or more pistons.

The logic of the servocontrol can integrate the continuous opening of at least one of the two valves of each piston, so as to avoid sucking vacuum or compressing gas in the pipe of the piston. This arrangement avoids a breakage of equipment.

In the device illustrated in FIG. 1, an evaporation chamber 7 contains water to be purified. The evaporation chamber 7 comprises an inlet for receiving the water to be purified, not shown in FIG.

 A condensation chamber 8 contains the purified water. This chamber comprises an outlet for extracting the purified water not shown in FIG.

The engine-cylinder chamber 5, the evaporation chamber 7 and the condensation chamber 8 may be connected to vacuum pumps referenced respectively 9a, 9b and 9c. The chambers can also be connected to one and the same vacuum pump.

The evaporation chamber may be placed in thermal contact with a hot source SC.

 The condensation chamber may be placed in thermal contact with a cold source SF.

The operation of the device is as follows:

 Water to be purified is introduced into the evaporation chamber 7 via the inlet provided for this purpose.

If the engine-cylinder chamber 5, the evaporation chamber 7 and the condensation chamber 8 are connected to vacuum pumps 9a, 9b, 9c, it is possible to suck the air from these chambers 5, 7, 8. It is thus possible to ensure in the three chambers 5, 7, 8 that the pressures are below atmospheric pressure and substantially identical to each other before the piston system 3, 4 is operated, or while said system is in operation.

 The pressures are considered substantially identical if they differ by less than 50 millibars.

 There is a transitional phase during which the air of the chambers 5, 7, 8 is sucked.

 During the transient phase, the temperatures in the three chambers 5, 7, 8 can change.

 These temperature variations can generate pressure variations in the three chambers.

 The vacuum pumps 9a and 9b can ensure during the transient phase that the pressures in the two chambers 5 and 7, 8 remain substantially identical to each other.

The device 6 for setting the pistons system 3, 4 into operation is turned on and the pistons 3, 4 describe the vertical cyclic trajectory each within its piston duct 1 January.

 The interface system is coupled to the piston system 3, 4, so that when a piston (3 or 4) rises the associated interface (1 respectively 2) is in the vertical position.

 Simultaneously, the other piston (4 respectively 3) goes down and its associated interface (2 respectively 1) is in the vertical position.

 FIG. 1 corresponds to a rising phase of the piston 4 and of lowering of the piston 3.

 During the rise phase of the piston 4, the volume above the water contained in the evaporation chamber 7 increases.

This produces a phenomenon of evaporation by depression. Purified water vapor is produced on the surface of the liquid water to be purified.

 This evaporation does not cause an increase in the temperature of the water and therefore there are no disadvantages related to the presence of hot water in this device.

 Part of this steam is sucked into the wake of the piston 4 which rises, When said piston 4 has arrived at the top of its trajectory, the coupling between the piston system and the mobile interface system acts on the movable separations.

 In particular, the interface 2 which was in the vertical position goes into a horizontal position.

 The steam sucked into the wake of the piston 4 which mounted in the piston duct 1 1 is then separated from the evaporation chamber 7 and brought into contact with the condensation chamber 8.

 The piston 4 which had reached the top of its path descends and displaces the steam of the piston duct 1 1 towards the condensation chamber 8.

In this way, the condensation chamber 8 receives purified water vapor alternately pushed by the piston 4 and the piston 3. Part of this vapor accumulated in the condensation chamber 8 goes into the liquid state. The liquid water obtained is a purified water.

The constant volume of the engine-cylinder chamber makes it easier to maintain and control the pressure exerted on one of the walls of each piston, in particular the piston wall located on the engine-cylinder chamber side. In this way, the energy required for the aspiration of the vapors can be controlled and decreased, thus decreasing the economic cost of the purification.

In particular, it becomes possible to set the pressure exerted by the engine-cylinder head substantially equal to the pressure exerted by the evaporation chamber. As a result, the energy associated with the displacement of a piston in the suction phase decreases and essentially contains only the contributions of friction, work of movement of the mass of pistons and moving parts associated with the movement of the pistons and finally the work of displacement of the mass of steam. If the evaporation chamber 7 and the engine-cylinder chamber 5 are connected to one or more vacuum pumps 9a, 9b, these chambers can be maintained at the same pressure Po.

 If the evaporation chamber 7 is in thermal contact with a heat source SC, thermal energy is supplied to this chamber throughout the operation of the system so that the temperature in this chamber can be maintained at a temperature To.

 A heat transfer can take place from the evaporation chamber to the engine-cylinder chamber, so that these two chambers are found at the end of a transitional phase at the same temperature To.

For example To can be between 5 and 50 degrees Celsius. To can be of the order of 27 degrees Celsius, that is to say between 26.9 ° C and 27.1 ° C.

 For example Po can be between 8 and 123 millibars. Po can be of the order of 36 millibars that is to say between 35.8 millibars and 36.2 millibars.

The condensation chamber 8 may comprise a thermal contact with a cold source SF at a temperature T _e lower than To.

The presence of a temperature zone T _e in the condensation chamber 8 makes it possible to increase the condensation phenomenon.

The thermal contact with the cold source SF also has an effect on the pressure which decreases in the condensation chamber 8.

If a vacuum pump 9c is connected to the condensation chamber 8 and initially the pressure has been adjusted in the condensation chamber at Po, then the pressure in the condensation chamber decreases in below of Po during a transitional phase. On each piston, the pressure exerted by the engine-cylinder chamber 5 becomes greater than the pressure exerted by the condensation chamber 8. This difference may persist throughout the operation of the system. In this situation the work of the pistons is facilitated in the phase of recovery of the vapors in the condensation chamber.

FIG. 1a is a diagram illustrating a device for purifying water, in particular salt water, a large part of the structure of which corresponds to that of FIG. 1. The device comprises a motor-cylinder chamber 5, comprising a device 6 for setting in motion a system of pistons which describe a vertical trajectory, ascent and descent within a piston duct 11.

 The device contains an evaporation chamber 7 and an evaporation chamber 8.

 The pistons 3A, 3B, 4A and 4B are associated in pairs, on the one hand the pair of pistons 3A and 4A, on the other hand the pair of pistons 3B and 4B. The two pistons of the same pair describe a movement offset by half a cycle with respect to each other.

 In the particular case of FIG. 1a, the piston 3b is at its highest position in its piston duct and begins a downward movement, whereas the piston 4B is at its lowest position in its duct. piston and starts a climb movement.

 If the piston 3A is in upward movement (ascending respectively) then the piston 4A is in downward movement (respectively descending).

Supply of salted water in the evaporation chamber

When the salt water level drops in the evaporation chamber, salt water can be reinjected, for example at the temperature To, for example at 27 ° C. This injection can be carried out in small amounts so as to increase the pressure marginally in the evaporation chamber and in the rest of the device. By "small quantities" is meant a volume of water corresponding, for example, to one-tenth of the volume of vapor drawn from the evaporation chamber during a period of travel of a cyclic trajectory by a piston.

 These injections are done either continuously or by spot injections or by combining these two modes.

 In this way, it is not necessary to stop the device to supply the evaporation chamber with water to be purified.

Evacuation of the purified water from the condensation chamber

 It is possible to use an airlock to ensure the evacuation of purified water. The chamber is a receptacle located at the bottom of the condensation chamber and composed of a lower part and an upper part.

 The volume of the lower part is smaller than the upper part and especially much smaller than the volume of the condensation chamber. There are two movable partitions: an inner partition between the lower part and the upper part, an outer partition between the lower part and the outside of the condensation chamber.

When the lower part is empty of liquid water, the outer partition is closed and the inner partition is opened so that the lower part is separated from the outside of the condensation chamber and communicates with the upper part and the condensation chamber. .

 Liquid purified water is created in the condensation chamber and accumulates in the lower part.

When the lower part is full, the inner wall is closed, then the outer wall is open. The purified water flows outwards and the lower part is again empty of liquid water. Again, the outer wall is closed and the inner wall is opened and a new cycle begins.

The air that fills the lower part when the purified water is emptied can be chosen at a temperature less than or equal to To, for example equal to T _e , and at a pressure less than or equal to Po. In this way, temperature and pressure in the condensation chamber can be kept constant during operation of the device.

 It is thus not necessary to put the device at a standstill in order to extract the purified water from the condensation chamber.

Piston comprising a deformable membrane

 The device as described above can be adapted so that each piston comprises a deformable membrane.

 When the pressure exerted on the piston is almost identical on both sides, it is not necessary to use a rigid piston. A piston of deformable material less mechanically resistant may be sufficient to move the steam.

 The deformable membrane can be arranged so that in its most deformed configurations, it is not fully stretched. This makes it possible to limit the wear of the membrane.

 Figure 2 shows such a piston.

 The piston 13, housed in the piston duct 1 1, separates the engine-cylinder chamber 5 and the evaporation chamber 7.

 The membrane which forms the piston 13 may be fixed at its outer perimeter for example in the middle of the piston duct 1 1, so that this perimeter can not be set in motion.

The force exerted by the device 6 for setting the piston system in motion applies to the center of the membrane of the piston 13 and imposes a deformation thereof. Figure 2 corresponds to a deformation of the membrane towards the evaporation chamber.

 The volume generated by the movements of the piston is obtained by the deformation of the membrane, or flapping of the membrane.

This makes it possible to reduce the friction associated with the movement of the pistons, and to reduce the mass set in motion during a cyclic trajectory.

The duct may be truncated at the desired level of attachment of the outer perimeter of the membrane, the upper part of the piston duct having no further use.

 To fix the membrane on the piston duct, several solutions are possible.

 A first possibility is to use glue.

 It is possible to choose an adhesive capable of fixing both elastomeric materials such as polyethylene and rigid materials such as steel.

 A second possibility is to tighten the membrane between the upper end of the piston duct and a frame.

 The assembly formed by the upper end of the piston duct, the membrane and the frame is tightened by a clamp-type device. Two seals can be added on each side of the membrane to prevent the metal from directly contacting the membrane and damaging it.

In the vicinity of the tight or glued area, the membrane may be reinforced with a thickness of 100 μm of LDPE.

Fixing the membrane on the piston duct can be performed so that even in the extreme positions of the membrane, it is not fully tensioned. This avoids asking too much of the membrane by successive deformations and to increase its duration of use before replacement.

It is also possible to use a deformable piston of low weight, for example with a deformable membrane consisting of a layer of polyethylene, preferably LDPE, preferably with a thickness of between 10 μm and 100 μm.

 The effect of a decrease in the weight of the piston is to reduce the energy required to set the piston in motion. This reduces the economic cost of operating the device.

 LDPE also has the following advantages:

 it is of common use and low cost

 It is known for its flexibility which makes it possible to use the beat of the membrane to obtain volume variations.

- LDPE has good heat sealability which allows to work with particular forms of membrane.

Of the standard thicknesses of LDPE, it is preferable to use a thickness of 30 μm or 50 μm because

- A thickness of 20 μm or less does not have sufficient strength

 A thickness of 100 μm and above does not give a sufficiently flexible LDPE. Preferentially, it is possible to use a LDPE derived from recycling.

It is possible to use square or circular membranes, that is to say whose outer contour takes the form of a square or a circle. The square shape makes it possible to install the pistons next to each other and to limit the unused surfaces to suck up the steam. This makes it possible to reduce the dimensions of the device. Piston comprising a deformable membrane which comprises an indeformable central portion

 It is possible to use membranes which have an indeformable central part. This dimensionally stable part follows the same movement as the center of the membrane driven by the device 6 for setting the piston system in motion.

Figures 3A and 3B show such pistons.

 The piston 23, housed in the piston duct 11, separates the engine-engine chamber 5 and the evaporation chamber 7.

The membrane which forms the piston 23 may be fixed at its outer perimeter for example in the middle of the piston duct 11, so that this perimeter can not be set in motion.

 The force exerted by the device 6 for setting the piston system in motion applies to the center of the diaphragm of the piston 23 and imposes a displacement of the non-deformable part and a deformation of the outer part of the membrane.

 Figure 3C schematically shows the volume generated by the movement of the piston in the situation where the portion of the membrane driven by the device 6 to set in motion is square. Other forms, such as for example a circular shape, of the dimensionally stable part can obviously be envisaged.

The volume swept during a trajectory cycle by this membrane is greater than in the absence of an indeformable central part. This allows to move more steam with the same return of the piston, while maintaining the absence of friction related to the movement of the pistons. The central part of the piston can be made indeformable by rigidly fixing it to a dimensionally stable structure.

 One can use a metal part, or a piece of polyethylene or another plastic sufficiently thick to be considered as deformable.

Figure 4 is a diagram illustrating an example of a deformable membrane structure 23 whose central portion is dimensionally stable and square.

The indeformable central portion 41 may be reinforced by a metal spider 43 whose ends are housed in fingers 42 made of polyethylene, preferably LDPE, heat-sealed to the membrane.

The ends can be used to define the shape of the central part. In particular, if the spider 43 has four ends of the cross defining a square, the indeformable central portion 41 has a square shape. According to a possible variant of the invention, it is possible to reinforce the metal spider defining a square shape with an outer hoop. In this way the indeformable inner part takes on a circular shape.

The metal spider 43 may comprise several branches each consisting of hollow aluminum round.

 The round hollow aluminum has a high rigidity, a great lightness and moreover does not fear contact with water vapor.

It is possible to use a hollow aluminum with a thickness of between 0.5 and 1.5 millimeters in thickness, preferably of the order of 1 millimeter. It is possible to use hollow aluminum rounds with a diameter of between 7 and 9 millimeters, preferably of the order of 8 millimeters.

 It is possible to strengthen the hollow aluminum round by solid sections, which does not significantly increase its weight.

Fingers with a thickness of between 70 and 130 μm, preferably of the order of 100 μm, may be used.

 Each finger can be welded on an area of the membrane that can itself be reinforced with LDPE 100 m to distribute the effort.

To make it easier to insert the metal spider into the membrane, it may be necessary for at least one branch included in the spider to be dismountable.

 The demountable nature of a branch can be achieved by dividing the branch into two pieces. The first piece may comprise a suitable screw pitch which collaborates with a clamping ring. The second piece comprises a stop of the clamping ring, so that by tightening the ring, the two pieces form a rigid assembly. A seal may be disposed in contact with the two pieces before tightening the ring.

Device materials

With the exception of the membrane, the aluminum spider, and certain parts of the device for moving the piston system, all the parts of the device may consist of high yield strength stainless steel sheets. .

 The stainless character makes it possible to resist the effect of water and in particular salt water.

The parts can be welded, or assembled by being separated by a seal so that they can be dismantled. The thickness of the sheets can be chosen equal to 4 millimeters, so that the device supports the pressure difference between the outside, which is at atmospheric pressure and the inside which can be for example equal to 36 millibars.

The parts of the piston system setting device which do not consist of high yield strength stainless steel plates are, for example, a crankshaft which is conventionally made of forged stainless steel, and rods which may be of aluminum .

Integration of the device into a cooling circuit of a power plant

Power plants consume fresh water.

A slice of plant needs 400 cubic meters of demineralized water daily. This water can come from seawater which is desalinated for example by reverse osmosis.

The power plants located at the seaside can use a cooling system that uses seawater as a coolant. Such a circuit comprises a fluid inlet cold path and a hot fluid outlet path,

 For example, the temperature of the cold input channel is 14 ° C, and that of the hot exit channel is 27 ° C.

The flow of such a circuit may be close to 60 cubic meters per second.

It is possible to integrate in such a cooling circuit a water purification device as described previously. Figure 5 is a diagram illustrating an assembly of a cooling circuit 110 of a power plant 100 and a device 10 for purifying water. The power plant 100 is cooled with water pumped at sea 200. The cold input channel 11 brings the seawater to the plant 100, and the hot outlet 112 takes the seawater to the water. 200 after it has been used to cool the central 100. It is possible to use the cooling system cold input inlet 111 as a cold source SF in the condensation chamber 8 of a cooling device. purification of water 10 according to the invention, and the hot outlet channel 112 of the cooling circuit fluid as a hot source SC in the evaporation chamber 7 of said device 10.

Said water purification device 10 can be used to supply demineralized water with a slice of the plant 100.

 This requirement amounts to 400 cubic meters of water per day, which represents 0.008% of the daily volume conveyed by the cooling circuit 110 of the plant 100.

 As this ratio is very low, the cold input channel 111 and the hot fluid outlet path 112 of the cooling circuit can be considered respectively as quasi-infinite sources respectively for cooling in the condensation chamber 8 and for heating in the chamber. of evaporation 7 of the water purification device 10.

In this situation, the energy required for evaporation in the evaporation chamber 7 can be provided by the hot fluid outlet path 112 of the cooling circuit via a heat exchanger. Such a configuration does not require the installation of a heat source, the hot outlet path being directly available on the site. This makes the system frugal overall, that is, the system consumes fewer resources than other systems of the prior art, such as the distillation type system.

In addition, the quantity of water to be purified can be taken from the hot fluid outlet of the cooling circuit

 For this purpose, an IN conduit connecting the evaporation chamber 7 and the hot outlet channel 112 may be installed so that a portion of the cooling fluid passing through the hot outlet channel 112 may be withdrawn and introduced into the chamber. evaporation 7.

The salt concentration of the liquid contained in the evaporation chamber increases as steam is drawn to the condensation chamber. It becomes necessary from a certain concentration threshold to act on this salt concentration to continue the purification.

 It is possible to regularly reject the liquid contained in the evaporation chamber to the hot fluid outlet path of the cooling circuit.

 For this, a line OUT connecting the evaporation chamber 7 and the hot outlet channel 112 may be installed so that a part of the fluid contained in the evaporation chamber 7 can be removed and introduced into the hot outlet channel 112. .

It is also possible to continue the production of steam to the point where the salt will partly precipitate, to recover the solid salt, and to reject the remaining liquid water to the hot fluid outlet of the cooling circuit. As the ratio of the flow of purified water to the flow of water conveyed by the cooling circuit of the plant is very low, the variation in salt concentration caused by the liquid discharges is very small.

 There will be no discharge of very salty water at sea.

More generally, when the flow of the cooling fluid through said cooling circuit is at least one hundred times greater than the flow of water purified by said device, the considerations mentioned above remain accurate.

In this situation, the cold required for condensation in the condensing chamber is provided by the cold fluid inlet path of the cooling circuit via a heat exchanger.

It can be estimated that for a production of 400 cubic meters per day of desalinated water as described:

 calorie sampling on the hot run to the evaporator leads to a drop of 0.04 ° C in this hot runner

 Likewise, on the cold side, the exchange with the condensation chamber leads to an increase of 0.04 ° C of this cold channel. Only the temperature drop in the cold path decreases the efficiency of the cooling system of the loss.

Example of a production of 400 cubic meters of desalinated water

A membrane is chosen of square shape of 0.5 meter side. A central non-deformable part is chosen square of 0.4 meter of side. With a LDPE thickness of 40 miti, one can expect a membrane beat amplitude of 0.20 meters.

 This gives :

a total suction volume of 0.0336 cubic meter. a mass of the moving part less than 100 grams

 a horizontal occupied surface of 0.6 meters by 0.6 meters, taking into account the dimensions of the movable membrane and the fixing area by gluing or clamping.

A speed is chosen to describe a cyclic trajectory of the piston of 10,000 cycles per minute. It is possible to achieve this speed because the moving parts are of low weight and the membrane does not withstand a significant pressure difference.

Using such a speed and a suction volume of 0.0336 cubic meters, a membrane produces a total volume of 336 cubic meters per minute.

It works with the elements described above including an inlet cold channel temperature equal to 14 ° C, and that of the hot outlet channel equal to 27 ° C.

It is desired to produce a volume of 400 cubic meters of liquid water per day. This corresponds to a volume of 15.38 10 ⁶ cubic meters of water vapor at 27 ° C per day, ie 641 10 ³ cubic meters of steam per hour, that is 10.6 10 ³ cubic meters of steam per minute.

To achieve this goal, 32 membranes must be used.

 Aligning the 32 occupied horizontal surfaces corresponding to the 32 square membranes according to a rectangle of 4 surfaces by 8, we obtain an overall surface of 2.4 meters by 4.8 meters.

These dimensions are smaller than the dimensions of some reverse osmosis installations already in operation, particularly in power plants. FIGS. 6A, 6B, 6C, 6D, 6E and 6F show a piston duct in a device for purifying water, especially salt water. This piston duct 211 comprises two pistons 23A and 23B whose movement modifies the volume of air in which the vapors evolve above the evaporation chamber or above the condensation chamber. This volume of air is located in the center of the piston duct 211 between the pistons 23A and 23B. The pistons 23A and 23B are synchronized in their movement so that they increase together (FIGS. 6A, 6B and 6C) or reduce together (FIGS. 6D, 6E and 6F) the volume of air in which the vapors evolve above the evaporation chamber or above the condensation chamber.

 Each piston 23A, 23B is matched with a piston not shown in FIGS. 6A, 6B, 6C, 6D, 6E and 6F, which has the same trajectory in a movement offset by half a cycle.

The arrangement corresponding to a piston duct as shown in FIGS. 6A, 6B, 6C, 6D, 6E and 6F can be derived from the arrangement of the pistons as represented in FIGS. 1 or 1a.

 For this, the rotary movement generated by the movement device around a horizontal axis 6, and in particular perpendicular to the axis of the piston duct, can be transformed into rotary movement about a vertical axis and in particular parallel to the axis of the piston duct, by angular gearing or by displacement of the motor.

Claims

claims 1. Device for purifying water (10), in particular salt water, comprising an evaporation chamber (7) comprising an inlet for receiving a volume of water to be purified and providing a vapor suction phase, a condensation chamber (8) comprising an outlet for the purified water and ensuring a phase of purification. vapor recovery, characterized in that it comprises a gas transfer apparatus comprising an interface system delimiting movable separations (1, 2) between the two chambers, a piston system (3,4) coupled to the interface system for moving the movable partitions (1, 2) to order, a motor-cylinder chamber (5) containing a device (6) for setting in motion said piston system (3, 4), all the pistons describing a cyclic trajectory, the pistons (3, 4) being associated in pairs, two pistons of a pair describing the same trajectory in a movement offset by half a cycle with respect to each other, so that the setting in motion of the pistons is adapted to maintain a constant volume of the cylinder-chamber (5), the evaporation chamber (7), the engine-cylinder chamber (5), the condensation chamber (8) being connected, at least during a phase transient, to one or more vacuum pumps (9a, 9b, 9c) so that on each piston, the pressure exerted by the engine-cylinder chamber (5) is substantially equal to a pressure Po exerted by the evaporation chamber ( 7). 2. Device (10) according to claim 1 characterized in that all the pistons (3,4) describe the same cyclic trajectory, the positions of the pistons (3,4) being regularly distributed in the cycle of movement. 3. Device (10) according to any one of claims 1 to 2 characterized in that on each piston, the pressure exerted by the engine-cylinder chamber (5) is greater than the pressure exerted by the condensation chamber (8) . 4. Device (10) according to any one of claims 1 to 3 characterized in that the evaporation chamber (7) comprises a thermal contact with a hot source (SC) at the temperature To. 5. Device (10) according to any one of claims 1 to 4 characterized in that the condensation chamber (8) comprises a thermal contact with a cold source (SF) at a temperature T _e less than To. 6. Device (10) according to any one of claims 1 to 5 characterized in that the temperature To is between 5 and 50 degrees Celsius, preferably of the order of 27 degrees Celsius. 7. Device (10) according to any one of claims 1 to 6 characterized in that the pressure Po is between 8 and 123 millibars, preferably of the order of 36 millibars. 8. Device (10) according to any one of claims 1 to 7 characterized in that each piston (13) comprises a deformable membrane. 9. Device (10) according to claim 8 characterized in that the deformable membrane consists of a polyethylene layer, preferably LDPE, preferably with a thickness between 10 pm and 100 pm. 10. Device (10) according to claim 8 or 9 characterized in that the membrane has a square shape. 1 1. Device (10) according to any one of claims 8 to 10 characterized in that the membrane has a central portion (41) dimensionally stable. 12. Device (10) according to claim 1 1 characterized in that the central portion (41) is reinforced by a metal spider (43) whose ends are housed in fingers (42) made of polyethylene, preferably LDPE, heat-welded to the membrane. 13. Device (10) according to claim 12 characterized in that the fingers (42) have a thickness between 70 and 130 pm. 14. Device (10) according to claim 12 or 13 characterized in that the areas of the membrane heat sealed to the fingers (42) of polyethylene are reinforced by a LDPE thickness of between 70 and 130 pm. 15. Ensemble comprising a cooling circuit (1 10) of a power plant adapted to use seawater as a coolant comprising a cold fluid inlet (1 1 1) and a hot fluid outlet (1 12) a device (10) according to any of claims 1 to 14 adapted for: the flow of the cooling fluid through said cooling circuit (1 10) is at least one hundred times greater than the flow of water purified by said device (10), the condensation chamber (8) is in thermal contact with a part of the cold input channel (1 1 1), the evaporation chamber (7) is in thermal contact with a part of the hot outlet (1 12), one or more ducts (IN, OUT) connect the evaporation chamber and the hot outlet channel so that a portion of the cooling fluid passing through the hot outlet channel can be removed and introduced into the evaporation chamber, and that a part of the liquid present in the evaporation chamber can be removed and introduced into the hot outlet channel. 16. A method for purifying water, especially salt water, characterized in that it is implemented by a device (10) according to one of claims 1 to 14 and comprising the following steps:  Supply of water for purification in the evaporation chamber (7);  Operating a hot source (SC) to raise the temperature of the evaporation chamber (7); Operating a cold source (SF) to create a temperature zone T _e in the condensation chamber (8);  Evacuation of the air in the evaporation chamber (7), the condensation chamber (8) and the engine-cylinder chamber (5) to reduce the pressure;  Piston system (3,4) and coupled interfaces (1, 2) are set in motion, according to the following cycle for each piston and coupled interface: o Isolation of the condensing chamber (8) through the interface; o Suction of the steam from the evaporation chamber (7) by the piston; o evaporation chamber insulation (7) of the piston through the interface; o Recovery of steam in the condensation chamber (8) by the piston; Condensation of the vapor in the temperature zone T _e in the condensation chamber (8). 17. Process for purifying water according to claim 16, in which: The evacuation of the air in the evaporation chamber (7) and the engine-cylinder chamber (5) reduces the pressure to the same pressure value. in these two rooms. 18. A method for purifying water, especially salt water, characterized in that it is implemented by an assembly according to claim 17 and comprising the following steps:  Supply of water to be purified in the evaporation chamber (7) by removing a portion of the cooling fluid passing through the hot outlet (112);  Stabilizing the temperature of the evaporation chamber (7) at the temperature of the hot exit channel by thermal contact with a portion of the hot outlet channel (112);  Stabilizing the temperature of the condensing chamber (8) at the temperature of the output cold path by thermal contact with a portion of the output cold path (111);  Evacuation of the air in the evaporation chamber (7), the condensation chamber (8) and the engine-cylinder chamber (5) to reduce the pressure;  Piston system (3,4) and coupled interfaces (1, 2) are set in motion, according to the following cycle for each piston and coupled interface: o Isolation of the condensing chamber (8) through the interface; o Suction of the steam from the evaporation chamber (7) by the piston; o evaporation chamber insulation (7) of the piston through the interface; o Recovery of the steam in the condensation chamber (8) by pushing the piston; Condensation of the steam in the condensation chamber (8). 19. A method of purifying water according to claim 18 wherein: a portion of the liquid present in the evaporation chamber (7) is removed and introduced into the hot outlet (112) when the salt concentration of the liquid present in the evaporation chamber (7) exceeds a predetermined threshold.