FR2561637A1 - Process and device for producing distilled water from seawater - Google Patents

Abstract

Process and device for producing distilled water from seawater, in which a flow of seawater 10 is heated by solar radiation in a greenhouse system consisting, for example, of a line of floating caissons 3 communicating with each other to permit the flow of the heated water from one to the other, each caisson 3 comprising a glazed frame 6 mounted above a central bridge opening 7 of the caisson in order to expose the seawater circulating in the latter to solar radiation; the flow of seawater 10 entering via the first caisson 3a passes through the successive caissons 3 as far as a vacuum evaporator 2 in which it is distilled and from the exit of which distilled water is collected. This process permits a continuous production of distilled water with simple and inexpensive means during the daylight hours in sufficiently sunlit regions.

Description

 The present invention relates to a method and a device for producing distilled water from sea water, during daylight hours.

 In accordance with the process targeted by the invention, sea water is heated by means of solar radiation by greenhouse effect, the flow of sea water thus heated is channeled to a vacuum evaporator in which the flow the heated water is first evaporated. then condensed, and the distilled water obtained is collected at the outlet of the evaporator.

 According to a feature of the invention. this process being implemented on a sheltered marine surface, such as a harbor or a basin, the water vapor is condensed on a condenser cooled by sea water pumped into the surrounding sea.

 The device for implementing this method comprises a greenhouse system capable of floating on the surface of sea water, at least part of its upper surface is transparent to solar radiation, and inside which can enter a surface layer of seawater which can thus be gradually heated, and a vacuum evaporator device into which a stream of seawater heated by greenhouse effect can penetrate, this device comprising a degassing chamber for the water of sea, an evaporation chamber and a condensation chamber, as well as means for collecting the distilled water at the outlet of the condensation chamber.

 The greenhouse system causes, by solar radiation, the rise in temperature of a flow of seawater flowing there. This heating is obtained gradually and continuously, so that at the outlet of the greenhouse system, at the inlet of the vacuum evaporator, an exploitable thermal difference is produced, of several tens of degrees. between the temperature of the seawater in the stream and that of the surrounding seawater, The circulation of the seawater stream from the inlet of the greenhouse system to the evaporator is initiated by 1 evaporation water in the evaporator.

 According to one embodiment of the device according to the invention, the greenhouse system is formed of a chain of floating caissons connected together so as to allow the circulation of a flow of seawater gradually heated from the first until at the last caisson, each caisson comprising a shell in which is formed a pipe allowing the circulation of the seawater flow, and at least one glazed frame disposed on this shell and authorizing the penetration of solar radiation into the caisson.

Other features and advantages of the invention will become apparent during the description which follows, given with reference to the accompanying drawings which illustrate several non-limiting embodiments thereof.
- Figure 1 is a perspective view of a first embodiment of the device for producing distilled water from sea water according to the invention;
- Figure 2 is a perspective view on an enlarged scale with respect to Figure 1 of a box of this device;
- Figure 3 is a top view of the shell of the box of Figure 2;
- Figures 4 and 5 are respectively in longitudinal elevation and at the end of the box of Figure 3;
- Figure 6 is a perspective view of a pipe forming part of the box of
Figures 2 to 5 ;;
- Figure 7 is a schematic elevational view of 1 vacuum evaporator apparatus forming part of the device according to the invention;
- Figures 8 and 9 are respectively perspective and side elevation views of a second embodiment of the box forming part of the device according to the invention;
- Figure 10 is a schematic perspective view of a third embodiment of the device according to the invention;
- Figure II is a longitudinal section view of the device of Figure 10.

The device represented in FIGS. 1 to 7 is intended for the implementation of a process for producing distilled water from sea water, on a sheltered marine surface such as a harbor or a basin,
This device comprises a greenhouse system capable of floating on the surface of seawater 1, at least part of its upper surface of which is transparent to solar radiation, and inside which a surface layer of water can enter. sea can thus be gradually heated. The device also comprises a vacuum evaporator 2, shown schematically in Figure 7, into which a stream of seawater heated by the greenhouse effect can penetrate, means being provided for collecting the distilled water at the outlet of the '' evaporator 2.

 The greenhouse system visible in Figure 1 is formed by a chain of floating caissons 3, interconnected so as to allow the circulation of a flow of seawater 10 progressively heated from the first caisson 3a to the last caisson 3b, and which open into 1 vacuum evaporator 2. Each box 3 comprises a shell 4 in which is formed a pipe 5 allowing the flow of sea water to flow, and at least one glazed frame 6 disposed on the shell 4, authorizing the penetration of solar radiation into the box 3. The frame 6 rests on a thermally insulated bridge 7, which itself rests on the upper edges of the hull 4 and of the pipe 5 housed inside the hull. The bridge 7 has a central orifice 8 under the glazed frame 6, so as to allow the penetration of solar radiation inside the box 4 and the pipe 5, which has a U-shaped profile open upwards.

The pipe 5 rests on the bottom and the sides of the shell 4 by means not shown, for example by spacers, and is thermally insulated from the shell 4, from which it can be separated by an air gap 9 as in the example shown, the shell 4 is provided at its two ends with coupling means 11 to the contiguous shells 4, forming connection fittings between the neighboring caissons 3, and allowing the circulation of the seawater flow from a box 3 to the next. The first box 3a is provided with a member 12 providing an inlet for seawater, for example a strainer (Figure 1), while the last box 3b of the chain opens into a degassing chamber 13 (Figure 7) of evaporator 2, by a connection 14.
U 5 of each box 3 is provided with means to facilitate the circulation of the seawater flow from one end to the other of the box, for example (Figure 6) of baffles 15 positioned on the bottom Sa of the pipe 5, parallel to the direction of F of the seawater current. The baffles 15 are further arranged so as to oppose the reflection of the solar light on the longitudinal walls 5b of the pipe 5 and its return to outside.

 The pipe 5, located in the plane of the waterline of the box 3, crosses the hull 4 from end to end, the bottom Sa being situated at a level lower than that of the waterline. but parallel to it. The upper parts of the sides 5b of the pipe 5 exceed the level of the waterline, and are connected to the internal face of the bridge 7, on either side of the central opening 8. Thus, the open upper part of the pipe 5 is placed just below the opening 8. At its ends, via the coupling members 11, the pipe 5 communicates with the ends of the pipes of the contiguous boxes 3. The seawater flow 10 coming from the pipe 5 of a box 3 located before the box 3 considered, flows through the pipe 5 of the latter, then enters by the coupling member 11 nearby, in line 5 of the following box. The sides 5b of the pipe 5 are thermally insulated, in order to limit the heat losses.

 The air gap 9 reserved between the pipe 5 and the shell 4 further strengthens the thermal insulation of the box.

 The shape of the hull 4 is designed to ensure the buoyancy of the box 3 and its balance thanks to ballasts 20. and to be able to contain the pipe 5 in which the seawater flow 10 must circulate.

 Furthermore, on deck 7. the base 12 circumscribes the central orifice 8, the empty part of the key 12 superimposed on the orifice 8. The base 12 is thermally insulated, and supports the chassis 6, in principle planar . which is composed in a manner known per se of a glazing and a rigid frame 17 supporting the glazing. The latter can be made of glass, or of transparent synthetic material, capable of replacing glass. The chassis 6 covers and closes the orifice 8 of the bridge 7, is supported on its base 12 with an inclination determined by the search for maximum insolation, and is placed directly above the pipe 5. It is of the so creates a closed area delimited by the pipe 5 and by the internal faces of the bridge 7, the base 12 and the frame 6, this closed area forming a greenhouse.

 The solar radiation after passing through the glazed frame 6 enters this closed area and causes, by greenhouse effect, the heating of the sea water contained in the pipe 5, this heating gradually increasing from the first box 3a to the following boxes.

 As a possible alternative embodiment, several glazed frames such as 6 and not just one, can be placed on the deck 7 of a box 3. they are then arranged so as to overhang the pipe 5, by as many corresponding openings . Similarly, for the sake of efficiency, the chassis 6 can be made mobile, and can then rotate above the orifice 8 of the bridge 7, by means of suitable mechanical members, known per se. Thus, the glazed frame or frames 6 can be oriented towards a determined point on the horizon, in order to follow the movement of the sun.

 At the outlet of the last box 3b, the heated seawater 18 (Figure 7) enters the evaporator device 2, which operates in a manner known per se, in application of the CARNOT principle. The evaporator 2 makes it possible to obtain, under vacuum and continuously, the evaporation and condensation of the sea water heated by several tens of degrees relative to the water outside the chain of wells 3, in n ' using for this purpose only a small temperature difference between the cold pole and the hot pole. The evaporator 2 mainly consists of three chambers: the degassing chamber 13, under partial vacuum, an evaporation chamber 18 and a condensation chamber 19, both under relatively high vacuum. Pumps 21, 22 maintain the desired voids in the respective chambers 13, 18 and 19. The evaporator 2 is placed on a platform, not shown, floating or fixed, at the end of the chain of caissons 3. The chamber degassing 13, thermally insulated, communicates with the evaporation chamber 18 through a conduit 23 located under the level N of the water in the degassing chamber 13. In the condensation chamber 19. cooling is provided by a condenser 24 supplied with water extracted from the surrounding sea by a pump 25, at room temperature. The base of the chamber 19 opens into a pipe 26 for discharging distilled water, equipped with a pump 27, the distilled water being able to be collected in a storage tank 28. The chambers 18 and 19 are separated by a vertical partition 29, delimiting with the upper part of the chambers a passage opening 31 for the water vapor obtained by evaporation of the heated sea water 32, in the chamber 18.

The heated sea water, coming from the chambers 3, enters the chamber 13 where it loses the air in suspension which it contains. Then introduced into the evaporation chamber 18, the sea water 32 evaporates there under the effect of the vacuum, then passes in the form of vapor (arrow G), in the chamber 19 where it condenses in distilled water on the condenser 24. During this phase, the steam can be used to actuate a turbine (not shown) at low pressure, to obtain energy,
After its condensation, the distilled water is evacuated by the pump 27 and the pipe 26 to a storage place. by any suitable means such as tray 28.

 The distillation operation could have the consequence of bringing into the evaporation chamber 18 an unacceptable concentration of salt. In order to overcome this drawback, part of the heated seawater introduced into the chamber 18 is not evaporated, but is evacuated via a pipe 33 by means of a pump 34, with the addition of salt. This water could possibly be used in an exchanger. A balance is established between the flow rate of the evaporated water and that of the discharged water, the total of these flow rates determining that of the seawater flow which circulates inside the chambers 3 and of the evaporator 2.

 Furthermore, the sea water used to cool the condenser 24 can, after passing through the exchanger, be used as a source of preheated water. As such, it can be introduced in whole or in part into the chain of caissons 3, through the inlet orifice of the first caisson 3a. In such a variant, the inlet caisson 3a should then be placed near the outlet evaporator 2. This water then follows the evaporation process described above.

 In the second embodiment of the device shown in Figures 8 and 9, each box 35 is equipped with a glazed frame 36 mounted to tilt on its base 37 so that it can be raised or lowered like a shutter. The periphery of the chassis 36, rectangular in this example, is integral with a rigid telescopic hood 38 whose end opposite to the chassis 36 is fixed to the base 37, which is thermally insulated and mounted on the deck 7 of the box 35. The face the interior of the hood 38 is reflective in order to reflect the solar radiation passing through the chassis 36 towards the central orifice 8 of the bridge 7, regardless of the angular position of the chassis 36 relative to a horizontal plane.

 This angular position is adjustable using means not shown. and the base 37 can be rotatably mounted on the bridge 7 around a vertical axis.

 Thanks to the internal reflecting surface of the hood 38. the solar radiation, after having passed through the chassis 36, is reflected on the central orifice 8, regardless of the angular position of the chassis 36 relative to the horizontal plane. Furthermore, the mobility of the chassis 36, in the horizontal and vertical planes, enables it to adopt, facing the sun, a position of maximum exposure. This maintenance of the chassis 36 in an optimum exposure position is ensured permanently, by servo motors not shown, whose action compensates with respect to the sun, the effects of the rotation of the earth.

 A possible alternative embodiment consists in using a movable reflector in order to return the sunlight onto the glazed frame. In this event, the reflector goes by mechanical or other means, programmed, can rotate during the day, around the chassis 36, reflecting the solar radiation towards the latter, according to a determined incidence.

 In the third embodiment of the invention illustrated in Figures 10 and 11. the floating greenhouse comprises two membranes 39, 41 substantially horizontal and superimposed. secured by a network of spacers 42, 43 which maintain an appropriate gap between the two membranes 39, 41. The upper membrane 39 is transparent and maintained above the surface S of the seawater flow, while the membrane lower 41 is opaque, thermally insulated and located below the surface S.

 The upper membrane 39 is provided with an insulating peripheral skirt LS, bent downwards so as to extend into seawater to a level lower than that of the lower membrane 41.

The skirt 44 thus defines with the membrane 41 a continuous passage 45 for the entry of sea water to be heated between the membranes 39, 41, and prevents the heated water from escaping towards the outside. The upper membrane 39, made of a suitable transparent material, for example a plastic material, is kept extended on the surface of the sea by a set of suitably distributed floats 46, or by any other suitable means of flotation. The membranes 39, 41 are made integral by the spacers 42, 43 which maintain the desired distance between them and ensure their perfect spreading on the surface and under the surface of the sea.

 The surface occupied by these membranes can be as large as the configuration of the site chosen allows, the shape of the occupied surface can be approximately round for example, without this shape being decisive. The evaporator 2 is preferably placed in the geometric center of the covered surface (Figure 10).

 The seawater enters through the opening 45 between the membranes 39 and 41, then flows in a laminar flow, between the two membranes to the central evaporator 2 which sucks it up. During its movement between the membranes 39, 41, the seawater flow is heated by 1 action of the solar radiation passing through the upper membrane 39, the heated seawater, naturally placing itself above the cold water. not being able to cross towards the outside the peripheral skirt 44 acting as a barrier. The heated seawater thus remains circumscribed within the limits of the device and is pumped by the vacuum evaporator 2 to which it is directed, possibly guided by baffles not shown, After reaching the evaporator 2, l heated seawater begins the evaporation process described above.

 The invention is not limited to the embodiments described and can include numerous variant embodiments. The method and the device according to the invention make it possible to produce continuously. during the daytime hours and in sufficiently sunny regions, water distilled from sea water, with relatively simple and inexpensive means compared to the means currently known.

Claims (9)

 1 - Process for producing 1 distilled water from sea water, characterized in that sea water is heated by solar radiation by greenhouse effect, the flow (10) of water is channeled sea water heated up to a vacuum evaporator (2) in which the flow of heated water is first evaporated. then condensed, and the distilled water obtained is collected at the outlet of the evaporator (2).  2 - Method according to claim 1, implemented on a sheltered marine surface, characterized in that the water vapor condenses on a condenser (24) cooled by sea water pumped into the surrounding sea.  3 - Device for implementing the method according to one of claims 1 and 2, characterized in that it comprises a greenhouse system capable of floating on the surface of 1 sea water, at least part of its upper surface is transparent to solar radiation, and inside which can be # a surface layer of sea water which can thus be gradually heated, and a vacuum evaporator (2) into which can penetrate a flow (10) d sea water heated by greenhouse effect, this apparatus comprising a degassing chamber (13) of sea water, an evaporation chamber (18) and a condensation chamber (19), as well as means for collecting distilled water at the outlet of the condensation chamber (19).  4 - Device according to claim 3, characterized in that the greenhouse system is formed of a chain of floating boxes (3) connected together so as to allow the circulation of a stream (10) of heated sea water progressively from the first (3a) to the last box (3b), each box 13) comprising a shell 14) in which is formed a pipe (5) allowing the circulation of the flow (10) of sea water, and at least a glazed frame <5) disposed on this shell (4) and authorizing the penetration of solar radiation into the box (3).  5 - Device according to claim 4, characterized in that the pipe (5) of each box (4) is thermally isolated from the shell (4), from which it can be separated by an air gap (9), this pipe <4) has a U-shaped section open upwards and on which is placed an insulated bridge (7) supporting the glazed frame (s) (6), the latter (s) being suitably oriented ( s) to receive solar radiation, and the shell of each box 13) is provided at its two ends with means 111) for coupling to the adjoining shells (4) to allow the circulation of the flow (10) of sea water d 'one box (3) to the next, the first box (3a) comprising an inlet opening for seawater while the last box (3b) of the chain opens into the degassing chamber (13) of the evaporator (2).  6 - Device according to claim 5, characterized in that the pipe t5) of each box (3) is provided with means to facilitate the circulation of the flow (10) of sea water from one end to the other of the box (3), for example baffles (15) positioned on the bottom <Sa) of the pipe (5), parallel to the direction of the current, and arranged so as to oppose the reflection of sunlight on the walls (5b ) from the pipe (5) and its return to the outside.  7 - Device according to one of claims 4 to 6, characterized in that the glazed frame (36) is pivotally mounted on its base so as to be able to rise or lower like a shutter, and its periphery is secured d '' a rigid telescopic hood (38) whose end opposite to the glazed frame (36) is fixed to a thermally-insulated base (37), mounted on the deck (7) of the box (35), the internal face of the hood (38) being reflective in order to reflect the solar radiation towards a central orifice <8) of the bridge, and this whatever the angular position of the frame (36) relative to a horizontal plane, this angular position being adjustable and the base < 37) for supporting the chassis which can be rotatably mounted on the bridge (7) about a vertical axis.  8 - Device according to claim 3, characterized in that the floating greenhouse comprises two membranes (39, 41) substantially horizontal and superimposed, secured by a network of spacers (42, 43) maintaining an appropriate gap between the two membranes (39 , 41) in which a laminar flow of sea water can take place, and capable of being kept extended on the surface of the sea by flotation means such as floats (s6), the upper membrane (39) being transparent and maintained above the surface of the seawater stream while the lower membrane (41) is opaque, thermally insulated, and located below the surface of the seawater stream.  9 - Device according to claim 8, characterized in that the upper membrane (39) is provided with an insulating peripheral skirt (44), bent downward so as to extend in sea water to a level below that of the lower membrane (41) and at a certain distance from the edge of the latter, in order to delimit with said lower membrane <41) a continuous passage (45) for entering the sea water to be heated and preventing the heated water from escaping to the outside, and the vacuum evaporator (2) of the heated seawater flow is preferably placed in the central region of the membranes 139, 41), means for discharging the distilled water obtained being connected to the evaporator (2).