WO2012025656A1 - Seawater desalination unit - Google Patents

Abstract

The invention relates to a seawater desalination unit comprising frames provided with reverse osmosis membranes (1) that are connected to salt water and desalinated water collection circuits (2) inside a submersible chamber (3) joined to a counterweight base (5) including coupling means (6) for immersion and hoisting purposes. The aforementioned chamber (3) is connected to: a desalinated water outlet pipe (7) containing a first pump/tank (9); a brine outlet pipe (8) containing a second pump/tank (10); and at least one salt water inlet including a suspended-particle filter (4, 11, 12, 13), said chamber (3) being placed at the depth necessary for osmosis to occur.

Description

 Marine Water Desalination Unit

 OBJECT OF THE INVENTION

 The present invention, as expressed in the statement of this specification, consists of a seawater desalination unit whose essential purpose is to provide an alternative to land desalination plants, taking advantage of the pressure generated at the seabed to separate the water of the solutes instead of resorting to the application of electrical energy or to the artificial generation of differences in ground pressures, for which the invention facilitates a structure with racks provided with reverse osmosis membranes inside a chamber that is submerged to the depth necessary for osmosis to occur, in order to initiate the process of separation of water and solutes with an energy efficiency comparable to or greater than that of the desalination units of the prior art.

 BACKGROUND OF THE INVENTION

 We know several registers referring to systems for desalination of seawater such as the Spanish patent with publication number 2,112,206 and enunciated as "system with fixed or mobile lift for desalination of sea water with reverse osmosis cell device, submerged at variable depths of work"; as the Spanish utility model with publication number 1.070.065, enunciated as "seawater desalination and pumping unit"; as the French patent No. 2,484,391 enunciated as "process and device for the production of fresh water from seawater"; or as US Patent No. 3,060,119 set forth as "conversion of salt water into drinking water".

As these records reflect, the technique of desalinating seawater through structures with reverse osmosis membranes is known, using the high pressures of deep sea waters to facilitate corresponding osmotic exchange in these membranes, which, subject to the different internal and external pressures of an enclosure closed by them, allow pure water to pass in a direction, but not the salts in solution that may exist.

 This use of the pressure in the deep sea has energy advantages compared to the production of the necessary pressures on the mainland, since it is necessary to artificially effect the aforementioned pressure difference.

 Among the records cited, we consider patent 2,112,206 and utility model 1.070065 as closest to the present invention. In the first case, as stated in its summary, it is a system for desalination of seawater by means of a device consisting of one or more modules with high resistance to pressure and corrosion that, having the appropriate Number of reverse osmosis cells is submerged at great depths of work. All this supported either by ship, platform or any other fixed or propelled system, the latter being able to act both as a physical support for the pressure modules and for the different systems for transferring desalinated water obtained in depth to the surface; of central storage, distribution and supply, being able to represent an alternative to conventional plants, even in economic performance.

As can be seen in the figures of said patent, the practical embodiment of this system is a kind of spherical capsule where the osmotic exchange is carried out and which is connected to a ship by means of cables and conduits. Although the system of this patent with publication number 2,112,206 uses the same technology as the present invention, it is a very different structure from that of the present invention; being also excessively generic the protective scope defined by the part characterizing the first claim of that patent, so that it does not bring any novelty to the state of the art that was known before 1996, year of application for this patent 2,112,206, as can be demonstrated with US Patent Document 3,060,119 aforesaid.

 On the other hand, with respect to the utility model 1.070.065 it is worth mentioning that the characterizing part of its first claim indicates that "it comprises one or more deep-submersible reverse osmosis units consisting of steel tubes with semipermeable membranes inside and anchored on the seabed so that desalination can occur due to sea pressure itself, which have prefilters, brine removal tubes, lead weights, anchors for fixing to the seabed, and steel cables connected to a platform or floating buoy for control and maintenance, said reverse osmosis units being directly connected by tubes to one or more submersible tanks to which desalinated water passes and these connected by tubes to a water pump that pumps water from the tanks to maintain the pressure difference between the deposits and the osmosis units.

Although in this utility model there are some of the elements of the present invention, such as pumping devices, reservoirs and filters, the structure and functionality arrangement of said elements, even without being well detailed in the corresponding document, it is seen that It is remarkably different from that of the present invention, requiring in the two embodiments that said document shows a system for the use of the force of gravity nonexistent in the system of the invention, referenced as 1 in this utility model. In addition, the tanks 3 used by this utility model are either submerged at the level of the reverse osmosis units 2, according to the embodiment shown in figure 1, or floating at sea level, as shows Figure 2 of the second embodiment in said utility model, and not at particularly suitable intermediate depths as can be seen in the structure of the present invention. In addition, this utility model of the state of the art also presents the drawback indicated for the patent of not providing novel technical characteristics that facilitate an efficient and viable system in the desalination of seawater by means of pressure changes due to deep dives.

 DESCRIPTION OF THE INVENTION

 To achieve the objectives and avoid the inconveniences indicated in previous sections, the invention consists of a seawater desalination unit that has racks provided with reverse osmosis membranes that use the high pressure of the deep sea waters to facilitate the corresponding osmotic exchange in the referred membranes.

 Novelly, according to the invention, said racks are connected to connector circuits of saltwater and desalinated water inside a submersible chamber attached to a counterweight base with hook and loop hitching means; said chamber being connected to: an outflow conduit of desalinated water in which a first pump tank is inserted; a brine outlet pipe in which a second pump tank is inserted; and at least one salt water inlet with suspended particulate filter; the aforementioned camera being located at a first value of marine depth, which is the depth necessary for the reverse osmosis process to occur, which according to preferred embodiments is around 700 meters with current technology.

According to a preferred embodiment of the invention, said hooking means consist of rings that can be connected to lifting and immersion chains. In addition, in said preferred embodiment of the invention, the first reservoir-pump is located at a second depth value, which is the depth necessary for fresh water to accumulate, and is equivalent to approximately 10 to 20 m less than the depth at which the chamber is located. This depth is equivalent to a pressure value between 1 and 2 bars. According to preferred embodiments, this depth at which the first pump tank is located is around 680 meters. The said second pump tank is located at a third depth value, which is approximately the depth necessary for the pressure value to be approximately 65 bar lower than the pressure at the place where the chamber is located, and which preferably is approximately 650 m less than the depth at which the chamber is in the preferred embodiment.

 On the other hand, in the aforementioned preferred embodiment of the invention, the said salt water inlet with filter is selected from:

 - one or more openings with respective filters in the camera body itself; both in the upper part of the chamber and, optionally and additionally, in the lower part,

 - the aforementioned one or more openings with filters in the body of the chamber plus an additional opening of the chamber that is connected to a salt water line that ends in an additional filter of suspended particles for salt water inlet.

 Another characteristic of the preferred embodiment of the invention is that said additional filter of particles of the saltwater conduit is located at a fourth depth value that is 60 ± 10% m of the sea surface.

Furthermore, this additional particle filter of the preferred embodiment of the invention is installed in an arrangement selected from: free immersion to said fourth depth value, and connected by means of a cable or link to a marine platform, boat, cliff, coast or other surface station.

 On the other hand, according to various embodiments of the invention, some, several or all of said pipes are capable of incorporating buoyancy elements that prevent their sinking.

 In addition, in the seawater desalination unit of the example of the invention the location thereof is selected from:

 - location parallel to a cliff, so that the brine conduction is arranged vertically and after leaving the said second tank-pump flows freely into the atmosphere on the sea surface; while the conduction of desalinated water, also arranged vertically, after leaving the said first pump-tank flows into the terrestrial surface of the cliff by means of a bend for its use or re-distribution to the distribution or supply network after its mineralization;

 - location in close proximity to the marine coast, so that the brine conduction is arranged vertically and after leaving the said second pump tank flows freely into the atmosphere on the sea surface; while the conduction of desalinated water after leaving the said first pump tank is carried to the coast on the seabed with the natural inclination that overcomes the corresponding slope for its use or reconduction to distribution or supply network after its mineralization;

- location under marine platform or vessel, so that the brine conduction is arranged vertically and after leaving the said second pump-tank flows freely on the said platform or vessel; while desalinated water conduction, also arranged vertically, after leaving the first pump-tank referred to the platform or vessel for use or storage. With the structure described, the invention has advantages relative to the use of gravity and the pressure of the sea depths as energies that allow the development of the reverse osmosis process without the need to create artificial structures that generate the corresponding pressure. Another advantage of the invention is that it facilitates mobile units without requiring large-scale land structures, so that its environmental and urban impact is very low or zero. On the other hand, by means of the desalination unit of the invention there is no deterioration or destruction of the areas or ecosystems where it is included, leaving that area or ecosystem with the same environmental characteristics as those that existed prior to the installation of the unit. The invention has advantages relative to the fact that the operating costs are relatively small as large structures are not needed for its development. The invention overcomes problems of the state of the art by providing a structure that optimizes energy efficiency, facilitating the most convenient conduits and depth values for a seawater depth desalination unit.

 Next, in order to facilitate a better understanding of this descriptive report and as an integral part thereof, some figures are attached in which the object of the invention has been shown as an illustrative and non-limiting nature.

 BRIEF DESCRIPTION OF THE FIGURES

 Figure 1.- Represents a schematic elevation view of a seawater desalination unit made according to the present invention.

Figure 2.- Represents a schematic profile view of the seawater desalination unit of the previous figure 1. Figure 3.- Represents a top plan view and schematic of the desalination unit of the previous figures.

 Figure 4.- It is a schematic view of the desalination unit of the previous figures 1 to 3 in a first application in which it has a location parallel to a cliff.

 Figure 5.- It is a schematic view of the desalination unit of the previous figures 1 to 3 in a second application in which it is disposed with a location in proximity to the marine coast.

 Figure 6.- Represents a schematic view of the desalination unit of the previous figures 1 to 3 for a third application in which it has a location under a marine platform or vessel.

 DESCRIPTION OF AN EXAMPLE OF EMBODIMENT OF THE INVENTION

 Next, a description of an example of the invention is made with reference to the numbering adopted in the figures.

 First, we provide a list of the numerical references of the six figures in this document indicating their meaning:

 1: Racks with reverse osmosis membranes.

 2: Collector circuits of desalinated water and brine. 3: Chamber or rack enclosure 1.

 4: Openings with filter in the chamber 3.

 5: Camera base-counterweight 3.

 6: Chain hitch rings 19.

 7: Desalinated water conduction.

 8: Brine conduction.

 9: First tank-pump for desalinated water extraction.

10: Second tank-brine extraction pump. 11: Additional opening of seawater entry into chamber 3. 12: Conduction of seawater connected to the additional opening 11.

 13: Additional water inlet filter in line 12.

 14: Marine surface.

 15: Cliff.

 16: Marine coast.

 17: Boat.

 18: Attachment cable of the additional filter 13 in the boat 17.

 19: Lifting and immersion chains of the base-counterweight

5.

 As can be seen in Figures 1, 2 and 3, where elevation, profile and plan views of the desalination unit of the present example are shown schematically, the frames with reverse osmosis membranes 1 are connected to water collecting circuits salt and desalinated water 2 inside a submersible chamber 3.

 Said frames 1, as well as circuits 2, are made of materials that have high resistance to pressure and corrosion, such as stainless steel. In chamber 3, the pressure is equalized by the entry of water through the openings with filter 4, so that a large structural reinforcement in said chamber 3 is not necessary.

 The chamber 3 is jointly and severally connected to a counterbalance base 5 that can be made of reinforced concrete and which includes hooking means consisting of rings or rings 6 that facilitate the engagement of chains 19 to facilitate immersion and lifting of the unit , as can be seen in Figure 6.

In addition, the chamber 3 is connected to an outflow conduit of desalinated water 7 in which a first pump tank 9 is interleaved, to an outflow path outside of brine 8 in which a second tank-pump 10, and several salt water inlets provided with suspended particulate filter.

 Said several saltwater inlets with filter consist in the present example in openings with filter 4 made in the body of the chamber 3 and in an additional opening 11 that extends in a conduction of seawater 12 outside the chamber 3 until finished in an additional filter 13, as can be seen in figure 1.

 This additional filter 13 may or may not, according to various applications, be connected by means of a connecting cable or link 18 to a surface station or vessel 17, as can be seen in Figure 6.

With the structure that has been explained, the technique of using the desalination unit of the present example consists in introducing the chamber 3 with its associated elements about 700 m deep so that the seawater that reaches the racks 1, free of particles in suspension, by virtue of the additional filter 13 and the filters of the openings 4, it reaches the racks 1, so that once the osmotic exchange has occurred, the desalinated water rises by the conduction 7 approximately 20 m from the location from the chamber 3 to 700 m deep, so that a distance of another 650 m would be missing to bring it to the surface. At the same time, the brine rises by conduction 8 about 650 m with respect to the situation of the chamber 3 at 700 m deep, with what would be approximately 50 m to take it to the marine surface 14. In order to complete the natural climbs of brine and desalinated water, the first and second pump-reservoirs 9 and 10 are used at convenient depths, as can be seen in figure 4. Thus, the first pump-tank 9 is disposed approximately 680 m below the surface marine 14, while the second pump tank 10 is arranged approximately 50 m deep with respect to the marine surface 14, all of which the chamber 3 is about 700 m deep with respect to said marine surface 14, as shown in Figure 4.

 On the other hand, the additional filter 13, with the depth values referred to above for the pump tanks 9 and 10 and for the chamber 3, is located at a depth of approximately 60 m below the sea surface 14.

 To calculate the internal diameters of the pipes 7 and 8, as well as the capacities of the tanks 9 and 10 and the strength of their respective pumps, estimates are made of the water flows to be extracted with the desalination unit of the specific application .

 To introduce the hollow conduits of the desalination unit at the mentioned depths, it is necessary to calculate the weight of the liquid that will be dislodged and counteract it with a mass that develops the opposite thrust.

 at this force, with which the mass that the base-counterweight 5 must have with the chamber 3 is calculated. In addition, the introduction into the water of the unit must be carried out at a controlled speed so that the corresponding functional structures are not damaged, This is done through the anchors that facilitate the rings 6 connected to the chains 19, which will serve both for immersion and for lifting the desalination unit.

The openings presented by the chamber 3 in the present example are three or four depending on the needs of the salt water inlet and air outlet that has been calculated, and can be seen in Figures 1 and 2 three openings with filter 4 plus the additional opening 11 with the additional filter 13, which were mentioned above. In the body of the chamber 3 itself there must always be some opening to allow the entry of salt water from the beginning of the immersion process of the chamber 3 and thus allow its filling facilitating the process. The filters of the openings 4 and the additional filter 13 free the water from desalination of coarse particles such as sand, aquatic flora and fauna or others, so that the salt water passes into the chamber 3 clean of impurities by exerting pressure on the semipermeable membranes of the frames 1, and upon reaching the necessary depth, the process of separation in desalinated water and in brine begins by means of the reverse osmosis process, whereby the desalinated water of each frame 1 passes to a part of the corresponding circuits 2 to the desalinated water until reaching the conduit 7 at the height of the first pump tank 9, being pumped from there artificially to the surface. For its part, the brine resulting from the aforementioned process is collected in another part of the circuits 2 to flow into the conduit 8, rising to the level of the second tank-pump 10, being pumped from there to the surface.

 Figure 4 represents the comments for the application with a location parallel to a cliff 15, which turns out to be the ideal case of applying the unit of the present example, since the desalinated water outlet can be connected directly to a supply network after the necessary mineralization process, so that in this application of Figure 4 the energy and materials expenditure is minimal compared to two other applications that are explained below.

Another application is to arrange the unit with a location in proximity to the marine coast 16, which results in all analogous to the previous application, with the exception that the desalinated water conduction 7 is carried with the inclination corresponding to the natural level instead in vertical, adding in this case some structures such as floats that prevent the sinking of the pipes, resulting in this higher application in materials and energy for the extraction of desalinated water. Another application is shown in Figure 6, in this case with the unit arranged in a location under marine platform or vessel 17, as shown in Figure 6. In this case, the unit is located on the deck of the vessel 17, and by means of a crane and engine system, the corresponding immersion is carried out, so that the unit is installed on the vertical of the ship or vessel 17 that will serve as an installation platform, desalinated water tank and transport from it to a distribution network or mothership for filling other transport ships. The expenses in this application are small since the desalination unit is located on the vertical of the boat 17, the energy expenditure being somewhat greater than that of the unit parallel to the cliff 5, but with the advantage in this application of the boat 17 , that the investment in structures is not subject to a physical space, being able to serve different points; the additional advantage being given that the brine resulting from the process is not regularly poured into the same point or zone, thus being less damage to the natural conditions of the environment where it is poured. On the other hand, the necessary change of racks and the mobile nature of the installation allow periodic revisions that facilitate maintenance.

Other applications and examples of the invention are equally possible, such as on a fixed platform located above ground, or about 20 m deep, or even at a depth of about 700m. It could even take advantage of the oil rig tunnels that no longer serve to build a plant according to the invention. The desalination unit can work with current technology or with other more efficient technologies that produce the energy needed for the osmosis process. It has been estimated that without amortization of materials, with pumps of 25,000 1 / h and using a mid-range generator on the market, the cost per liter of desalinated water, using the desalination unit of this example in the application used by vessel 17, It places less than 30% of the cost per liter of an efficient conventional land desalination plant that is around € 0.31 per liter. It is estimated that using a small boat of 50 m of length, 10 m of beam and draft of 4 m with full tanks; for a consumption of 150 1 per person per day, a population of 8,000 people could be supplied with water. With a 100 m long vessel, some 30,000 people could be supplied, and with a 150 m long ship around 90,000.

Claims

 1. - MARINE WATER DESALATING UNIT, which has racks equipped with reverse osmosis membranes (1) that use the high pressure of the deep sea waters to facilitate the corresponding osmotic exchange in the said membranes; characterized in that said frames (1) are connected to salt water and desalinated water collector circuits (2) inside a submersible chamber (3) attached to a counterweight base (5) with coupling means (6) for immersion and hoisting; said chamber (3) being connected to: an outflow conduit of desalinated water (7) in which a first pump tank (9) is inserted; a brine outlet pipe (8) in which a second pump tank (10) is inserted; and at least one salt water inlet with suspended particulate filter (4, 11, 12, 13); the aforementioned chamber (3) being located at the depth necessary for osmosis to occur.  2. - Marine Water Desalination Unit, according to claim 1, characterized in that said hooking means consist of rings (6) connectable to lifting and immersion chains (19).  3. - MARINE WATER DESALING UNIT, according to claim 1 6 2, characterized in that the first pump tank (9) is located at a second depth value equivalent to the depth at which the pressure is between 1 and 2 bars and the referred to second tank-pump (10) is located at a third depth value and that is the depth at which the pressure value is approximately 65 bar less than the pressure at the place where the chamber is located. 4. MARINE WATER DESALATING UNIT, according to any one of the preceding claims, characterized in that said salt water inlet with filters is selected from:  - one or more openings with respective filters (4) in the chamber body (3) itself,  - the aforementioned one or more openings with filters (4) in the chamber body (3) plus an additional opening (11) of the chamber (3) that is connected to a salt water line (12) that ends in a additional filter (13) of suspended particles for salt water inlet.  5. Marine seawater desalination unit, according to claim 4, characterized in that said additional particulate filter (13) of the salt water pipe (12) is located at a fourth depth value that is 60110% m of the surface navy (14).  6. Marine seawater desalination unit, according to claim 4 6 5, characterized in that that additional filter of particles (13) of the salt water pipe (12) is installed in an arrangement selected from: free immersion to said fourth depth value , and connected by a connecting cable or link (18) to a marine platform, vessel (17), cliff (15), coast (16), or other surface station.  7. - MARINE WATER DESALATING UNIT, according to any one of the preceding claims, characterized in that some, several or all of said pipes (7, 8, 12), according to applications and installation of the desalination unit, incorporate buoyancy elements that prevent its sinking  8. - Marine Water Desalination Unit, according to any one of the preceding claims, characterized in that the location of the desalination unit is selected from: - location parallel to a cliff (15), so that the brine line (8) is arranged vertically, and after leaving the said second pump tank (10) flows freely into the atmosphere above the sea surface (14); while the conduction of desalinated water (7), also arranged vertically, after leaving said first tank-pump (9) flows into the terrestrial surface of the cliff (15) by means of an elbow for its use or redirection to the distribution network or supply after mineralization;  - location in close proximity to the marine coast (16), so that the brine conduit (8) is arranged vertically, and after leaving the said second pump tank (10) it flows freely into the atmosphere on the marine surface (14) ; while the conduction of desalinated water (7) after leaving said first tank-pump (9) is carried to the coast (16) on the seabed with the natural inclination that exceeds the corresponding slope for its use or reconduction to the water network. distribution or supply after mineralization;  - location under the marine platform or vessel (17), so that the brine conduit (8) is arranged vertically and after leaving the said second tank-pump (10) flows freely onto said platform or vessel (17); while the desalinated water line (7), also arranged vertically, after leaving the first tank-pump (9) flows onto the platform or vessel (17) for use or storage.