MXPA98004725A - Desalination of a - Google Patents

Abstract

The present invention relates to: A desalination plant (10) which includes a pump pair to pump water at a pressure of between 50 and 65 bar to a filter element (30) generally cylindrical which includes a plurality of membranes of reverse osmosis that define salt ducts. Immediately upstream of the filter element (30) there is a disk (40) with a plurality of holes (44) therein. The disk (40) forms an obstruction that causes a pressure drop between the current-upstream side thereof and the downstream side. It also divides the fluid from the water into a series of separate jets which invade the end of the filter element and flow the salt ducts. The downstream water of the obstruction is not only lower than the upstream water pressure of the obstruction but also of turbulent fluid. The disc (40) and the filter element (30) are in a cylindrical box (12). The brine that emerges from the filter element, and which still has a substantial pressure, can be fed to a medium such as a Pelton turbine to recover some of the residual energy of the filter.

Description

WATER DESALINATION Field? Je application of7. invention This invention relates to the desalination of water, ie the removal of dissolved solids in seawater and brackish water. Background to the invention Discussions regarding the global shortage of drinking water and irrigation are common. In some parts of the world, entire cities must be abandoned due to prolonged droughts. The only inexhaustible water supply is the sea, but the desalination of water in significant quantities, to provide populated centers or large irrigation projects, is expensive. Many desalination plants work based on reverse osmosis. In this type of plant, the water to be desalinated is driven through a semipermeable membrane so that the dissolved solids are removed by the membrane. Other plants operate on the basis of evaporation. A major problem in both methods described is that the water obtained is, in the case of the evaporation method, pure distilled water and, in the reverse osmosis method, it is of the same degree of purity as the distilled water. Virtually all the minerals that were dissolved in the water have been removed. Water without any calcium or magnesium content binds metal pipes and other metal objects with which it makes contact. Therefore, these minerals have to be added to the reclaimed water. In addition, distilled water has no flavor, lacking essential minerals and can not be used for human consumption for prolonged periods. Therefore, for drinking purposes, it is necessary * add a range of minerals to convert 'tasteless' water into acceptable drinking water. In both described methods the essential minerals that were in the sea water, are found in the brine that is a by-product of the process. A significant cost in the production of water from any of the types of plant is therefore the cost of the minerals that must be "re-introduced into the water and the necessary equipment" for this purpose. of evaporation, the energy needed to evaporate seawater is also significant when calculating the costs per megalitre of reclaimed water.The membranes of reverse osmosis are of combined constriction and one of the most frequently used forms comprises two films of a polymeric resin In the pipe there is an element to induce turbulence in the flow, the element is usually a welded mesh of plastic filaments, an amount of these membranes are wound in complex form on top of each other. a central tube, the water that passes through these films enters spaces between adjacent membranes and flows into the tube The tube has openings in its wall to allow the water ^ .Wt regenerated between the tube. The brine, that is, the residue of the seawater and the bulk of the dissolved solids, goes out through multiple salt ducts to a residual deposit or to a salt recovery plant. It is admitted, by those who work in this technique that on each side of said salt duct, and immediately adjacent to each film, there is a layer of concentrating polarization. These layers, which are of multi-molecular thickness, contain a concentration of dissolved solids higher than the bulk of the flow in the part of the salt duct at medium distance between the films. The element that induces the turbulence is intended to reduce the thickness of the polarization layer by concentration and thereby improve the capacity of the osmotic membrane, according to the current state of the art will have a rejection rate of dissolved solids of 99.3%. The dissolved solids that pass through the membrane are composed mostly of common salt, since their molecules are smaller than the molecules of most other minerals. A percentage of 0.7% represents 400-500 parts per million of dissolved solids in the reclaimed water, depending on the initial salinity of the seawater and is below the threshold at which the solids impart taste to the water. Embedding of osmosis membranes * Reverse is a serious problem and you will have to take measures that increase the cost of water, to inhibit the incrustation and remove it when it occurs. Encrusting may occur due to mineral deposits in the membrane or due to organic growth. By way of example, before the seawater reaches the membrane, it is treated with an inhibitor such as sodium hexametaphosphate (commonly known as co-shrimp). This limits the calcium and magnesium precipitation in the membrane, in the form of calcium and magnesium carbonates, but adds another factor of cost increase. Membrane manufacturers recommend a relatively low flow rate (water flow through the membrane in liters per hour per square meter of membrane) to avoid rapid scaling. The countercurrent washing of a membrane, that is, causing the water to flow in the reverse direction through the salt ducts, is a normal procedure to remove the scale. If a membrane is badly incrusted it has to be removed from the regeneration plant and subjected to multiple treatments in order to remove the scale. In extreme cases the incrustation can not be removed and the membrane will have to be thrown away. As a result of all these factors, water produced in a reverse osmosis plant is more expensive than water obtained by purifying water from an accumulation reservoir or a river. Then, despite the global water shortage, only a small percentage of the world's water is produced using osmosis plants to desalinate seawater. OBJECT OF THE INVENTION The main objectives of the present invention are to improve the efficiency of the reverse osmosis process, to significantly reduce the cost of the water produced by the reverse osmosis process, to inhibit the incrustation of the reverse osmosis membranes and to produce water with a content of suitable minerals, without the need for aggregates. BRIEF DESCRIPTION OF THE INVENTION According to one aspect of the present invention, there is provided a reverse osmosis desalination plant, comprising a filter element composed of reverse osmosis membranes that define salt ducts, a pump for pumping water to desalinate to said filter elements and an obstruction in the path of the water flow between said pump and said filter element, to introduce turbulence into the water stream, thereby causing a pressure drop through the obstruction, whereby the water downstream of the obstruction, when it enters said filter element salt ducts it is at a lower pressure than the tap water-upstream of the obstruction and its flow is more turbulent than it was current-upstream of the obstruction. The obstruction is preferably in the form of a plate with multiple holes in it, whereby the flowing water is clogged and dispersed in a number of divergent conical jets each of which is at a lower pressure than the running water pressure. -Up the plate. The holes in the plate can be of different sizes or they can all be of the same size with respect to each other. In a preferred form, the plate has a circular disc shape and the holes are in a spiral arrangement about the center of the disc. In another embodiment, the holes are in a circular arrangement and in yet another shape the holes are located along lines radiating outwardly from the center of the disc.

^ I§? If desired, a series of valves can be provided which restrict the flow to vary the flow surfaces of the holes in the plate generated by the individual jets of water. According to yet another aspect of the present invention, there is provided a method for desalting water, which comprises pumping the water by desalting to a filter element composed of reverse osmosis membranes that define salt ducts that give rise to a pressure drop in the water flowing to the filter element and simultaneously introducing turbulence into the water flow and feeding the turbulent water to the lowest pressure inside the salt ducts of the filter element. In the preferred execution, the water is dispersed, by said obstructions, in multiple divergent jets of turbulent water of conical shape, which cause the pressure to fall and introduce the turbulence, colliding each turbulent jet on the filter element. It has been found that the inlet pressures that are in the range of 50 to 65 bar and a pressure drop between 1.5 and 2.0 bar provide the best results. The plant and the method, in accordance with the present invention, produce reclaimed water having acceptable levels of dissolved solids, i.e., mineral content. It is not necessary to add aggregates to the regenerated water, since they contain enough dissolved solids that give an acceptable flavor. In view of the fact that magnesium and calcium are present in the reclaimed water, it is not aggressive with respect to metal pipes and fittings and an aggregate of these minerals is not required. It is estimated that by introducing turbulently the water that is dripping into the salt ducts of the membranes, the concentration layer by resolved polarization decreased in thickness. This allows the flow rate to be increased without unduly increasing the incrustation. Still another effect is to allow the passage through the membrane of other minerals in addition to the common salt, while not increasing the amount of common salt in the reclaimed water to an unacceptable level. Experimental works have shown that, by varying the pressure drop and turbulence, for example by varying the size of the holes in the plate, when these are the ones that form the blockage, the passage of different dissolved solids through the plate can be achieved. of the membranes in controllable amounts. Therefore, by means of tests and experiments, that is by varying the pressure drop and the turbulence, water that carries predetermined amounts of dissolved solids can be regenerated. Another additional advantage is that the work >; ? Experimental has shown that the incrustation of the membrane is significantly reduced when turbulent water is delivered to it. The brine that emerges from a conventional reverse osmosis plant is heavier than seawater and therefore sinks if it is returned to the sea. However, the brine that emerges from the desalination plant, according to the present invention, when it is returned to the sea, initially rises in the form of a plume, instead of sinking. It has been found that the brine is aerated and it has been found that the aerating agent is oxygen. In addition there are bubbles of oxygen in the regenerated water. Tests have shown that there is more oxygen in the reclaimed water and in the brine than there should be based on the amount of oxygen dissolved in the seawater. The oxygen bubbles are small because, even downstream of the obstruction, there is a substantial pressure, for example 45 to 50 bar. The small bubbles in the turbulent water are supposed to play a role in reducing the thickness of the concentration layers by polarization. Bubbles also seem to play an important role in the prevention of membrane fouling. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and to show how it can be carried out, reference will now be made, by way of example, to the accompanying drawings, in which: Figures IA and IB together constitute a section along the axis of a desalination unit that is part of a desalination plant; Figure 2 is a section, in the same plane as the sections of Figures IA and IB, showing an end part of the unit, on a larger scale; Figure 3 is an elevation of a disk; Figure 4 is a section, in the same plane as Figure 2 and on the same scale, showing a modification of the unit of Figures IA and IB; Figures 5A and 5B illustrate additional discs; Figure 6 is a cross-section in the form of a diagram through a hand-operated desalination plant; Figure 7 illustrates in diagrammatic form a motor desalination plant; Figure 8 illustrates another desalination plant in diagram form; Figure 9 illustrates in diagram form a submersible desalination plant; Figure 10 illustrates in diagram form the general distribution of a water desalination plant; Figure 11 illustrates a submersible desalination plant; Figures 12A and 12B as a whole illustrate a desalination plant that is contained within a single outer box; Figure 13 illustrates a floating desalination plant; Figure 14 illustrates a pond and the corresponding piping system. Referring first to Figures IA and IB, the illustrated desalination unit is generally designated 10 and comprises a cylindrical case 12 with end caps 14 and 16 fixed at opposite ends thereof. An inlet pipe 18 for water containing dissolved solids, passes through the end cap 14 and feeds the chamber 20 with water. The pipe 18 is connected to the outlet of a pump (not shown in Figure IA), which is capable of delivering water, say, at a pressure of 50 to 60 bar. A brine outlet pipe 22 leads from a chamber 24 through the end cap 16. Lip retainers 26 and 28 surround the end caps 14 and 16 and seal between the covers 14 and 16 and the box 12.

The reference numeral 30 generally designates a reverse osmosis filter element that fits snugly within the box 12. The element 30 comprises a core structure 32 that includes a central tube 34 that forms the regenerated water outlet of the filter element 30. The tube 34, in which there are multiple holes 36, passes at one end thereof through the lid 16. The other end of the tube 34 rests in a blind bushing 38 (see also figure 2) provided for the purpose in a supporting plate having the shape of a disc 40. The disc 40 and the lid 14 form the confining walls of the chamber 20. A lip seal 42 surrounds the disc 40 between the disc 40 and the case 12. There is a gap between the disc 40 (see figure 2) and the filter element 30. The filter element 30 comprises, in addition to the ^ Core structure 32, a semi-permeable membrane that ^ is wound on the core structure 32. The rolled-up membrane fills the entire space between the core structure 32 and the inner face of the case 12, and except the gap between it and the disc 40, fills the space between the disc 40 and chamber 24. One type of commercially available filter element, which is suitable for use in the present invention is that manufactured and sold by Filmtec Corporation which is a wholly owned subsidiary of Dow Chemical Company. The product bears the designation FT30. U.S. Patent 4 277 344 describes in detail a membrane that works according to the principle of reverse osmosis. The winding of the membrane of the filter element 30 is complex. Initially this is formed by a series of flattened cells that are then rolled up on the core structure 32 in overlapping correlation. - Disk 40 (see figure 3) contains a series of eight holes 44.1, 44.2, etc. the holes vary in size and, in the illustrated embodiment, holes of 8,805 mm have been used, 9,185 mm, 8,077 mm, 7,772 mm, 7,675 mm, 7,351 mm, 7,094 mm, 7,881 mm. The diameter of the disc 40 is around 20 cm which is also the inside diameter of the box 12 and the outside diameter of the filter element 30. Behind the disc 40 and between it and the wound membrane, there is a star nut 46 (shown schematically in Figure 3) comprising a central horn, an outer ring and multiple spokes that go from the horn to the ring. The star 46 is part of the filter element that Filmtec delivers and defines a series of wedge-shaped openings. Each hole 44.1, 44.2, etc. it coincides with one of these openings, so that each jet of water impacts on the filter element. When the water drains under pressure through a restricted hole under pressure, the jet of water that comes out of the hole opens conically and then, at a certain distance from the hole, it fragments into droplets. The conical part of the water jet between the hole and the point at which the jet is fragmented is, in itself turbulent, presenting eddies and vertices. The filter element 30 is positioned so that the jets of water coming out of the holes 44.1, etc., impact on the filter element and drain into the salt ducts before they are fragmented in a rain of droplets. Fragmentation is inhibited, in the illustrated unit because, immediately after the water begins to drain, the gap between the disk 40 and the element 30 is filled with pressurized water. The applicant has found that the water delivered to the interior of the filter element 30, at the specific pressures described, does not have a dissolved solids content corresponding to an extraction of 99.3%, that is, the percentage extracted is less. With an inlet pressure of 50 bar and a disk 40 as described above, the system desalinates seawater to potable water that meets the standards established in the 'South African Bureau of Standards Specification 241 - 1984'.

Current-downstream of holes 44.1, 44.2, etc., pressures of the order of about 48.5 bar to 49.5 bar have a pressure in chamber 20 of about 50 bar. The applicant has also detected a very slight increase in temperature through the disk 40 and assumes that this result comes from the introduction of turbulence into the stream. The structure of Figure 4 differs from that of Figures IA, IB, 2 and 3, in that the different pressures on the downstream side of the disc 40 are achieved by regulations of a set of control flow valves 48 of the Water. The valves 48 include seals or diagrams for varying their effective flow surfaces and, together, constitute the obstruction that introduces turbulence and causes the pressure drop. Each valve 48 has a control cable 50 leading to it and each valve 48 is in a pipe 52. The pipes 52 are of the same diameter with respect to each other and pass through the disk 40. The valves 48 are electrically operated. and the amount of opening them can be controlled from a programmable controllers. The regulation of each valve 48 determines the pressure at the outlet of the corresponding pipe 52. By varying the pressure by means of the controller, the quantity of dissolved solids in the regenerated water is varied at will. Although the valves have been shown on the back of the disk 40, in another usable construction they can go inside the disk and next to the outlets from the holes in the disk 40. The disk 40 of figure 3 has its holes arranged in an array circular. In Figure 5B the holes are arranged in a spiral arrangement concentric with the disk. The spiral rotates in the same direction in which the filter element 30 is wound. In figure 5A the holes are arranged in a number of radial lines. The holes in Figures 5A and 5B are smaller than those shown in Figure 3 and are more numerous. Referring now to Figure 6, the desalination plant 54 illustrated operates by hand, comprising s a cylindrical box 56 in which there is a commercially available filter element 58, such as that described above and bearing the number 30 in Figures IA and IB. A retainer 60 surrounds the filter element 58 to prevent water from leaking between the case 56 and the filter element 58. Next to an end face of the filter element 58 there is a disc 62. Between the disc 62 and the case 56 there is a detent 64. The movement of the disc 62 to the left is prevented by a retaining ring 66. The holes in the disc 62 are not shown.

There is a gap between the disc 62 and the filter element 58. Adjacent to another end of the filter element 58 is a terminal stage 68 having a central tapped hole 70 and a secondary perforation 72 which is on one side of the perforation 70. The filter element 58, the disc 62 and the end cap 68 are as shown in FIGS. A and IB and therefore these components form a desalination unit 10. To the left of the disc 62 the box 56 forms a cylinder for a piston 80. The piston 80 includes a rod 82, which emerges from the case 56 through a sealing structure bearing the number 84. A nut 86 maintains the structure 84 in place. Two lip seals 88 and 90 and one ring-0 92 surround the piston 80. m ^ - A driving handle 94 is connected to a rod 82 by means of a sliding coupling (not shown). A coupling rod pivotally connects the handle 94 to a terminal plate 98 which, in turn, is secured to the flange 100 of the case 56. By oscillating the handle 94, the piston 80 can be moved alternately in forward and reverse strokes in its cylinder. The perforation 72 is connected, by a pipe 102, to a chamber 104 that surrounds the rod 82 and seals the structure 84. A check valve 106 allows the water to enter a chamber 108 that is between the disk 62 and the piston 80. The valve 106 is mounted in an opening in the wall of the casing 56. An outlet piping (not shown) is screwed into the tapped hole 70 and the reclaimed tap water flows from the tube 74 into this outlet piping. When the desalination plant illustrated in figure 6 is in use, the box 56 is fixed, with the valve 106 immersed in the salt water or brackish water to be desalinated. The upper end of the handle 94 is pushed or pulled to the illustrated position, which moves the piston 80 in its return stroke. When the piston moves to the left the valve 106 opens and the brackish or salty water is brought into the chamber 108. When the handle 94 is pushed to the left, the piston 80 begins its working stroke and moves towards the disc 62. The valve 106 closes immediately upon raising the pressure in the chamber 108. The water in the chamber 108 is driven through the holes in the disc 62, through the filter elements 58 and outwardly from the elements. of filter as potable water, via pipe 74 or as brine through bore 72 and pipe 102. The piston continues to the right until the lip seal 90 has passed the valve 106. After a few runs from the handle 94 the pressure starts to rise in the pipe 102 and then in the chamber 104. The forward stroke of the piston 80 is eventually aided by the pressure in the pipe 102 and the chamber 104. When the piston 80 ll At the end of its forward stroke, the lip seal 88 moves past the relief hole 110 and the pressure in the chamber 104 descends. Therefore there is no resistance to the return stroke of the piston 80, by any pressure in the chamber 104. The pressure necessary to drive the water through the filter element 58 and separate it into a flow of drinking water and a flow of brine , is in the order of 15 to 25 bar (for brackish water) and 50 to 60 bar (for sea water). The necessary pressure varies with the amount of dissolved solids in the water. The pressure loss in the filter element 58 is relatively small and the pressure of the brine in the pipe 102 can be 75% to 85% of the pressure there where the water enters the filter elements 58. This excess pressure , which otherwise would be lost, is used as described, to help operate the pump. Now looking at Figure 7, the illustrated desalination plant comprises a box 112 that has been arranged vertically. the ends of the box are closed by terminal lids 114 and 116 and there are detent rings (not shown) between the end caps 114 and 116 and the case 112. Immediately under the lid 114 there is a camera 118 and a disk 120. Under the disc 120 there is a filter element 122. There is a recess 124 between the disc 120 and the filter element 122. The filter element 122 has a central tube 126. The upper end of the tube 126 is located by the end cap 116. A Inlet pipe 128 leads into the interior of chamber 118. A brine outlet pipe 130 leads through terminal lid 116 and a potable water outlet pipe 132 passes through terminal lid 114 and connects to the upper end. of the tube 126. The disk 120 is, for example, of a configuration like that shown in Figure 3, Figure 5A or Figure 5B. The described components constitute a desalination unit 10. A vertically mounted pump 134 of the type 'Grunfos' has its suction inlet 136 connected by means of a filter 138 to a sea well or other water source that is to be desalinated. The pipe is connected to an outlet of the pump 134, with a control valve 140 installed in the pipe 128.

The pipe 130 is connected via a T-piece 142 and a control valve 144 to a drive turbine (Pelton) 146. The branch control of the T-piece 142 is connected, via a control valve 148 to a waste outlet 150 from where the brine is discharged to waste. The lateral outlet of the turbine 146 also discharges to residuals. The pump motor 134 is numbered 152. The power supply may comprise a direct connection to a network of 1220 volts or a connection to a solar panel 154, one battery 156 and an inverter 158. In the power supply circuit alternatively a control 160 is provided to allow varying the rate at which the motor 152 is driven. The central axis of the Pelton turbine is connected to the motor control shaft 152. As indicated above with reference to figure 6, there is a fall pressure inside the filter element 122, but the brine leaving the filter element 122 is still at a considerable pressure. By delivering some or all of the brine under pressure through the Pelton turbine, the power requirements of the engine 152 can be lowered, using some of the pressure energy that would otherwise be lost. In figure 8 a plant is represented that is similar to that of figure 7 and equal parts have been designated with equal reference numbers. Thus, the water to be desalinated enters at the bottom of the housing 112, instead of the top and the pump and motor (designated by the numbers 162 and 164 respectively) are not an integral unit. Instead, they are mounted side by side by means of their base plates 166 and 168. The pressure input in the box, # bearing the number 112, is by means of the pipe 128. The desalinated water comes out through the pipe 132 and the brine comes out through the pipe 130. The turbine 146 cooperates with the drive of the pump 162. The plant of desalination shown in Figure 5 9 comprises a vertical main box 170 that is placed at the bottom of the deep well in which there is water - ^^ T brackish or the bottom of a pool containing seawater. 172 shows a pump and motor which drives the pump is shown at 174. The pressure side of the pump is connected with a 0 chamber 176, the upper end of the chamber 176 being formed by a disc 178. Above the disc 178 is a filter element 180. Above the filter element 180 there is an end cap 182 which encloses a chamber between itself and the filter element 5 180. the brine exiting the filter element 180 enters this chamber and the regenerated water leaves the filter element 180 through a pipe 184. A Pelton turbine 186 is mounted in the box 170, on the terminal cover 182. The chamber between the terminal cover 182 and the filter element 180 is connected by a pipe 188 to the turbine. It will be understood that there is considerable pressure in the chamber. The brine entering this chamber under pressure, coming from the filter element 180 is delivered, through the pipe 188 and the Pelton 186 turbine, to a discharge pipe 190. The turbine 186 drives a pump (not shown). The pump is axially aligned with the turbine 186 and the pipe 184 is connected to the pump. The objective of the pump driven by the Pelton turbine is to raise the reclaimed water at ground level via a hollow column 192 (if the box 170 is in a deep well) or to the surface of the pool (if the box 170 is submerged in the saltwater pool). The motor 174 receives power from a set of solar panels 194 which are used to charge the batteries 196. A 220-volt power is shown at 198. This is connected to a step-down transformer and rectifier 200. It is also connected to a power unit. control 202 by which energy is fed to motor 174. Panels 194 and rectifier 200 attend to the charge of batteries 196. The output of batteries 196 is delivered through an inverter 204 that converts the output of 12 volts of EC, of the batteries at 220 volts a.c. A changeover switch 206 allows power to be taken from the inverter 204 or from the power supply 198, depending on which of these energies is available in the batteries. The control unit 202 raises the input voltage of 220 volts to an output voltage of 380 volts to power the motor 174. An advantage of the plant of Figure 9 is that only the reclaimed water is raised to the surface. The plant shown in Figure 10 comprises a box 208 with a built-in filter element 210 therein. The inlet for the water to be desalinated is at 212 and the outlet for the brine is shown at 214. The outlet for reclaimed water is shown at 216. The means for achieving the pressure drop upstream of the filter element 210 and to generate the jets of water that impact on the filter element 210 are shown equal to the shape illustrated in Figure 4. The water supply to be desalinated is shown at 218 and may be a seawater pool or a brackish water source. A feed pump is shown at 220, which draws water from feed 218 through a sand filter 222 and a disk filter 224. A high pressure pump is shown at 226, the side of the suction of the same it is connected to the filter 224 and the drive side to the inlet 212. The outlet 216 is connected to a vessel 228 in which the regenerated water is subjected to light . «, Ultraviolet (UV). The exposure of water to UV is a ^ standard procedure in water purification. The outlet from the container 228 leads to a storage pond 230. In case the plant is not going to be operated for a certain period of time, for example because there is sufficient stored regenerated water, there is a risk of bacterial growth and algae in the element 210. This can only be avoided by continuous circulation of water through the element 210. For this purpose. The tank 230 can be connected through a pump 232 and a valve 234 to the inlet 212. A valve 236 is closed when the valve 234 is opened. Using this circuit it is possible to continuously circulate regenerated water through the element 210 thereby ensuring the inhibition of bacterial growth. Since the pressure produced by the pump 232 is relatively low, there is a 'washing' action since the pressure is insufficient to force the water through the membranes and thus into the pond 230. The water * used for washing purposes It is discharged to residual. The brine outlet 214 is connected to a turbine 238 so that it is possible to take advantage of the residual pressure downstream of the filter element 210. The Pelton turbine can be used to pump reclaimed water or to generate electricity or to assist in the actuation of the rotor of any of the pumps 220 or 226. It is possible to incorporate flow switches 240 which indicate when the flow occurs in the pipe in which they are mounted and flow meters 242 that indicate the flow rate. The pH and conductivity of the reclaimed water can also be measured (in 244 and 246). All the information obtained is delivered to a general control 248 that exercises control over the entire system. Additional valves to allow closing the pipes in which they are installed, are shown in 250, 252, 254, 256, 258, 260, 262 and 264. To wash the disc filter 224 countercurrently, the valves 234 and 250 are closed and the valves 236 and 262 are opened. The water is thus removed from the tank 230 by the pump 232, delivered through the open valve 236, driven through the filter 224 in the reverse direction and discharged to waste through the open valve 262. * A level indicator 266 can be used in pond 230 to determine when the pond has been filled. The resulting signal can be used to shut off water withdrawal from feed 218 and initiate recycling through pump 232 and valve 234 to prevent bacterial growth. ^^ The torque of the turbine 268 can be controlled by incorporation of a torque indicator 270. If the torque increases above a certain predetermined level, the valve 256 opens so that some of the brine will bypass the turbine 268 and flow directly to residuals through the valve 256. The regulations of the valves that control the flow of water going to the filter element 210 can be maneuvered using the keyboard 272 of the type used with Pcs. The plant shown in figure 11 comprises a desalination unit 10 as shown in figure 1 placed vertically in a well. Equal parts have been designated with equal references. The inlet for the water to be desalinated is shown at 18, the outlet for the desalinated water is shown as connected to the pipe 34, and the brine outlet is shown at 22. A pump 276 is shown in Figure 11. The pump 276 is a hydraulic ram pump that works * vertically and that has its entrance at the upper end and its exit at the lower end. An outlet pipe has been designated 278 and there is an auxiliary pump 280 at outlet 278. The pump motor 280 is connected to a solar panel 282. The function of pump 280 is to start the flow through the pump. of water 276 and by discharging it through an outlet pipe 284. ^ The pump 276 includes flow control valves 286 and 288, one at the upper end of the pump and another at the lower end of the pump. When the pump 276 is blown, the resulting flow down through the pump 276, the resulting flow down through the pump 276 sucks the valve 286 into the open position and pushes the valve 288 into the closed position. When the valve 288 closes, a shock wave is transmitted through the pump 276. The shock wave drives the water under high pressure through a check valve 290 and into the interior of the inlet 18 of the box 12. another additional check valve 292 at the inlet 18. There is a diaphragm 294 connected to the valve 290. When the valve 290 is opened, the diaphragm is pushed through its central dead position. Once the shock has dissipated, the diaphragm 294 has the ability to close the valve 290 again.

The valves 286, 288 are connected by a rod 296 and therefore move in unison. Once the flow through the water pump has been started the pump 280 can be cut off by leaving it in an open condition, so that the flow can pass through it. The loading height of the water in the well (confined by the side wall 298 and the bottom wall 300) ensures that the pump 276 will continue its cycle. The residual pressure of the brine at the outlet 22 can be used for any of the purposes described above. It is convenient that the wall 298 divide the well relative to the sea. At high tide the water passes over the top of the wall 298 and fills the well 274. This provides the necessary loading height for the pump 276. When the tide goes down and no more water enters the well, the level in the well goes down regularly as the water drains through the water pump 276 and the outlet pipe 284. The submersible desalination plant shown in Figures 12A and 12B comprises a cylindrical box 302. Inside the box, and in at one end thereof, there is an electric motor 304 that moves the pump 306, the pump 304 can be of any suitable type, for example, a piston pump, an oscillating plate pump, etc. The saltwater inlet to pump 306 is not shown, but * the output bears the number 308. The output 308 is divided into two branches 310 and 312. The branch 310 leads to the core of a disk filter 318 which is contained in the cavity 320. A disk 322 forms one of the limits of the cavity 320 and on the other side of the disk 322 there is a filter element 324. The disk 322 can be described above with reference to figures IA, IB, 2 and 3 or Figure 4, or Figures 5A or 5B. The holes in the disk are not shown. The branch 312 leads directly into the interior of the cavity 320 and an outlet 326 leads from the core of the filter 318 through the disc 322. The outlet 326 contains a valve (not shown) that is normally closed. The disc filter 318 can be cleaned by closing the valve 314 and opening both the valve 316 and the valve 326 at the outlet. The water enters the cavity 320, from the cavity 320 passes through the disc filter 318, in reverse and outwardly through the outlet 326, removing any particles of dirt that have been trapped in the disc filter 318. Within the box 302 the regenerated water is subjected to ultraviolet light in a unit 328. According to what has been described above, the brine can be fed back to the motor pump so that the residual pressure can be used to decrease the energy needs of the motor 304 The power supply to the motor 304 can be as described above with regard, for example, to FIGS. 7 and 9. The floating desalination plant of FIG. 13 comprises a booth 330, an anchor block 332 secured to the seabed or that simply rests # on the seabed and an anchor cable 334 connecting the booth 330 with the anchor block 332. A horizontal division 336 divides a buoyancy space 338, which is located above the division 336 with respect to the intake chamber 340 which is below division 336. Holes 342 in booth 330 allow seawater to enter intake chamber 340. An electric motor 344 is mounted in such a way that, for the most part, it is located inside the chamber 340. On the motor 344 is mounted a pump 346 which is driven by the motor 344. The water is carried by the pump 346, from the chamber 340, through a filter 348. The pump outlet 346 is connected, by pipes numbered in conjunction with 350, to three units 10 of the type shown in Figures IA and IB. Although three units have been shown in booth 330, any appropriate number from one above can be used. The brine leaves from the units 10 through pipes 352 and is discharged to waste through an outlet 354. The regenerated water leaves through the pipes which together carry the number 356 and pass through an ultraviolet unit 358 for get to an exit 360. The plumbing system (not shown) goes from exit 360 to the beach and, in the shown embodiment, an electric cable (not shown) is laid from the beach, for the power supply of the motor 344. At the upper end of the booth 330 there is a solar panel 362 which is used to energize a light and a radio transmitter that together have the number 364. These elements are intended to warn the boats that transit in the area, of the danger that constitutes the floating plant. To make it unnecessary to deliver power to the plant and allow the engine 344 and pump 346 to be omitted, a piston pump can be provided between the car 330 and the anchor block 332. More specifically, a rod (not shown) it can come down from the cab 330 and carry a piston at the lower end thereof. A cylinder is mounted on the anchor block 332, the piston remaining inside a cylinder. The piston and the cylinder constitute a double or single action pump.

It is understood that the booth 330 will rise and fall in a measure that depends on the magnitude of the waves passing through its position. When raising the booth 330, it raises the rod and the piston with respect to the cylinder to which the anchor block prevents lifting. Therefore a lower cylinder chamber increases in size and can be filled with seawater through a tgy check valve. As the car 330 descends into a hollow between two wave crests, the piston moves down the box, reducing the volume of said lower chamber. Another check valve opens due to the increase in pressure in the lower chamber and the seawater is driven from the lower chamber into the pipe system 350. If desired, the piston rod can be hollow and this can conform the flow path from the lower chamber to the 350 system. The upper chamber of the cylinder can simply be opened to the sea. However, it is preferable that it also has an inlet check valve and an outlet check valve, so that the pumped water is pumped whether the piston is lowering with respect to the cylinder or when it is rising with respect to the cylinder. Finally referring to Figure 14, the reference numeral 366 designates a vertically elongated pond having a seawater inlet 368 through which seawater is pumped into the pond. The tank is open at its upper end to provide a vent 370. An outlet 372 is connected to the suction inlet of a pump that feeds water to the unit shown in Figures IA and IB. The water outlet regenerated from the unit of figures IA and IB is * g¡ ^ connected to the entrance 372 to the pond 366, so that ^ water, with a low concentration of dissolved solids in it, is returned to pond 366. Another exit can be seen 374 that allows the pond to be emptied and the solids it contains to be removed. In 376 an elongated glass peephole is shown. At the start-up of the desalination plant of which it forms a part, the tank 266 contains a volume of reclaimed water that is approximately equal to one third of the volume of water that may eventually be contained. The seawater is pumped in through the entrance 368 and the regenerated water is fed into the interior through the inlet 372. Water is then continuously drawn from pond 366 through outlet 372. Seawater entering through inlet 368 is diluted before leaving the pond through outlet 372. It has been found that although some of the water would regenerate It is recycled and not all reclaimed water is immediately removed from the plant, the total amount of separation of regenerated water increases and lesser pressures are needed to ensure that the harmful dissolved solids are removed from the water. Experimental work has shown that, even when regenerated water with a small content of dissolved solids can be delivered through the entrance 372, it is convenient to use a unit of # conventional desalination that provides water that is of the same quality as distilled water, as a source to be connected to inlet 372. It has also been found that a small amount can be added to the water produced by the method and apparatus of the present invention. of brine without increasing the common salt content to unacceptable levels. This procedure can be used, for example, where the conditions that will leave a sufficient amount of a certain mineral in the water can not be established. Supplementing the mineral that is not present in sufficient quantity with the addition of brine is, in such a case, a possible method to achieve the required mineral balance.

Claims (20)

R E I V I N D I C A C I O N S

1. A desalination plant by reverse osmosis, characterized in that it comprises: a filter element consisting of reverse osmosis membranes that define salt ducts; a pump for pumping water to be desalinated towards said filter element; and »an obstruction in the path of the water flow between the pump and the filter element to introduce turbulence into the flowing water and cause a pressure drop through the obstruction, whereby the running water-downstream of the obstruction, when it enters the salt ducts of the filter element it is at a lower pressure than the running water-upstream of the obstruction and its flow is more turbulent than what was current-upstream of the obstruction.

2. A plant, according to claim 1, characterized in that said obstruction has the form of a plate with multiple holes in it, whereby the water that flows is clogged and dispersed in a quantity of turbulent water jet, each of the which is at a pressure lower than the pressure of the running water - above the plate.

3. A plant, according to claim 2, characterized in that a series of valves that restrict the flow are provided, to vary the flow surfaces of the holes in the plate that generates the individual jets of water.

4. A desalination plant, according to claims 2 or 3, characterized in that it also includes: ar. a cylindrical box, in which the filter element It is inside the box and has been manufactured so that the inlets to the salt conduits are at one end of the filter element; a disc constituting the plate in which the disc is between one end of the box and the filter element and is separated from one end of the filter element; and an inlet for water to be desalinated at one end of the box, in which the water that enters the box, during operation, through the inlet flows through the holes in the disk, is dispersed in multiple jets of water. divergent water and one end of the filter element collides.

5. A desalination plant, according to claims 2 or 3, characterized in that it also includes: a cylindrical box, in which the filter element is inside the box and has been manufactured in such a way that the entrances to the salt ducts are in one end of the filter element; a disc constituting the plate, in which the disc is between one end of the box and the filter element and is separated from one end of the filter element; there is a pump inside the cylinder, and a motor to command the pump in which the pump is between the disk and one end of the box and serves to pump water to be desalinated, through the holes in the disk to disperse it in multiple jets of divergent water colliding on one end of the filter element.

6. A desalination plant according to claim 5, characterized in that it also includes a filter to remove the solid material from the water by desalting, in which the filter is between the pump and the disk.

7. A desalination plant, according to claim 6, characterized in that the pump has an outlet with two branches; in which the first branch leads through the filter to a chamber one of the ends of the disk constituted by the disk flowing the water normally through the holes in the disk and the other branch that passes in derivation with respect to the filter and that leads directly to the camera; in which there is a communication, normally closed, with the filter core; in which the outlet, when opened, allows the counter-wash water to flow from the chamber through the filter in the reverse direction and out through the outlet.

8. A desalination plant according to claims 2, 3 or 4, characterized in that it also includes: a cabin with at least one floating space to allow the cabin to float; in which the cylindrical box, with the contained filter and disk element, is inside the cabin; and in that the pump, in operation, delivers seawater under pressure to the box.

9. A desalination plant, according to claim 8, characterized in that the cabin is vertically elongated and has a horizontal division separating a water intake chamber below the partition with respect to a flotation space above the partition; in which the cabin contains holes to allow seawater to flow into the water intake chamber; and in that the pump in operation, extracts the water from the chamber and delivers it to the box that is in the flotation space.

10. A desalination plant according to any of claims 4 to 9, characterized in that it includes means for subjecting the regenerated water to ultraviolet light.

11. A desalination plant according to any of claims 1 to 4, characterized in that the pump is a hydraulic ram pump.

12. A desalination plant according to any of claims 1 to 4, characterized in that the pump is a manually operated piston pump for delivering pressurized water to the filter element.

13. A desalination plant according to any of the preceding claims, characterized in that it includes means for using the energy coming from the available pressure in the brine that emerges from the salt ducts, to supplement the energy source of the pump.

14. A desalination plant according to claims 1, 2, 3 or 4, characterized in that it includes: an outlet through which the regenerated water flows from the filter element; an auxiliary pump that has a suction inlet connected to the regenerated water outlet; a hollow column that emerges upwards from the auxiliary pump and is connected to the delivery outlet of the auxiliary pump; a brine outlet from the filter element; and a drive motor connected to the brine outlet, so that, in operation, the brine ~ r? under pressure it flows through the motor and drives it, being ^ the motor connected to the auxiliary pump in order to move 0 the auxiliary pump.

15. A desalination plant according to claim 14, characterized in that the drive motor is a Pelton turbine.

16. A method of water desalination, characterized in that it comprises: j F pumping the water by desalting to a filter element that is composed of reverse osmosis membranes that define salt ducts, resulting in a pressure drop in the Water flowing to the filter element 0 introducing, simultaneously, turbulence into the water flow; and feeding the turbulent water at a lower pressure inside the salt ducts of the filter element.

17. A desalination method, according to claim 16, characterized in that the water is dispersed in multiple divergent, turbulent water jets of conical shape by means of the obstruction that causes the pressure to fall and introduces the turbulence, each turbulent jet colliding on the filter element.

18. A desalination method, according to claims 16 and 17, characterized in that it includes the supply of seawater through a reverse osmosis membrane, to produce an auxiliary water supply substantially free of dissolved solids, or by mixing this water with seawater and delivering dissolved seawater to the filter element.

19. A method according to claims 16, 17 or 18, characterized in that it includes the addition of a certain amount of brine to the regenerated desalinated water, in order to modify the mineral balance of the regenerated water.

20. A method according to any of claims 16 to 19, characterized in that the water is initially at a pressure of 50 to 65 bar and the pressure drop is 1.5 to 2.0 bar. 0 5 RE S UM EN A desalination plant (10) is described which includes a pump for pumping water at a pressure of between 50 and 65 bar to a generally cylindrical filter element (30) which includes a plurality of osmosis membranes Inverse that define salt ducts. Immediately upstream of the filter element (30) there is a disk (40) with a plurality of holes (44) therein. The disk (40) forms an obstruction that causes a pressure drop between the current-upstream side thereof and the downstream side. It also divides the fluid from the water into a series of separate jets which invade the end of the filter element and flow into the salt ducts. The downstream water of the obstruction is not only lower than the pressure of the ijlpr "upstream of the water of the obstruction but also of turbulent fluid." The disk (40) and the filter element (30) they are in a cylindrical box 12. The brine that emerges from the filter element, and which still has a substantial pressure, can be fed to a medium such as a Pelton turbine to recover some of the residual energy thereof. 5