METHOD AND MEANS FOR DILUTING OR CONCENTRATING SOLUTIONS, APPLIED TO PROCESSES FOR THE DESALINATION OF WATER

Abstract

The invention relates to a method and means for diluting or concentrating solutions, applied to processes for the desalination of water, characterised by being carried out on the basis of a borehole (4) in permeable coastal land, where two internal wells (5, 6) are installed producing three channels that are interconnected at the bottom, by means of a membrane packet (9), disposed such that the supply flow towards the membranes and provided via the borehole (4) flows in a downward direction, generated, using the principle of communicating vessels, by the suction of a motor pump (7) installed at a shallow depth inside the well of the concentrate (5), with an ascending flow, pouring same to the marine outlet and the diluted flow (permeate) drains to the second well (6), which is hollow and at atmospheric pressure, where a motor pump (8) extracts the permeate for the use thereof. The method can be used for dilution and/or concentration with minimal energy costs, both on land and on the sea bed on a floating platform (11) or cliff.

Claims

1. A method for diluting or concentrating solutions preferably applied to processes for the desalination of seawater by means of reverse osmosis characterised in that it is carried out from a borehole (4) on a permeable coastal land, where, once it is developed by over-pumping, two internal wells (5 and 6) will be installed, producing three tubes which are interconnected on the bottom through a membrane packet (9), wherein the membrane packet (9) is arranged in a way that a feed flow, towards the membrane packet (9) and provided via the borehole (4), flows in a downward direction, generated because of using the principle of communicating vessels by means of the suction of a motor pump (7), which is installed at a shallow depth inside the well (5) of the concentrate with an ascending flow, pouring it to the marine outlet, and wherein a diluted flow (permeate) drains to the second well (6), which is hollow and at atmospheric pressure, where a motor pump (8) will extract it for the use thereof.

2. A method for diluting or concentrating solutions preferably applied to processes for the desalination of seawater by means of reverse osmosis, according to claim 1, characterised in that when the lands where the borehole goes through are not permeable, the seawater feed will be able to be carried out via the wellhead through a superficial layer with a filter bed connected to the sea, and wherein the well will be jacketed in its whole depth, sealing it, in order to avoid water losses and unwanted contaminations.

3. A method for diluting or concentrating solutions preferably applied to processes for the desalination of seawater by means of reverse osmosis, according to claim 1, characterised in that when the depth of the sea bed would be rather used instead of drilling the borehole, the tubes that form the wells (14) with their corresponding membrane packets (18) and motor pumps (4 and 18) are installed hanging from a floating platform (11) which is anchored to the sea bed through moorings (12), and wherein the permeate motor pump (8) will works in an inverted position in order to propel the water through the hose pipes placed on the sea bed that carry the water out to the coast.

4. A system for diluting or concentrating solutions applied to processes for the desalination of seawater by reverse osmosis characterised in that the system comprises: a borehole (4) on a permeable coastal land of around 450 metres; two wells: one well (5) of concentrate and another well (6) of permeate, which are both internal wells, located inside the borehole (4), and interconnected to each of three channels of a membrane packet (9); a membrane packet (9) that interconnects through its three channels the borehole (4) with each of the wells (5,6); a motor pump (7) which is installed at a shallow depth in the well (5) in order to extract the concentrate; and a motor pump (8) which is installed at the bottom of the well (6) in order to extract the permeate.

Description

DESCRIPTION OF THE DRAWINGS

[0031] In order to complete the present description for the purpose of helping to better understand the invention characteristics, the present memory is accompanied, as an integral part of it, by a set of drawings in which, with illustrative and non-restrictive purposes, the following is represented:

[0032] FIG. 1.It shows a section of a tubular membrane part by the longitudinal axis in which the direction of the existing three types of flows (channels) are shown in which the following marks can be seen:

[0033] Mark 1It represents the feed flow of the raw water to treat (100%) (channel 1).

[0034] Mark 2It represents the highest salt concentrate exit flow (90%) which is also called brine or rejected water that will supply the following membrane to in the end be returned to the sea through a marine outlet (channel 2).

[0035] Mark 3It shows the most diluted exit feed (permeate) that goes through the membrane and it flows through the central manifold of the membrane (channel 3).

[0036] FIG. 2.A general scheme of the method which is the object of the present patent is represented, in which the difference between the dynamic levels among the three wells can be seen with the following marks and meaning.

[0037] Mark 4It represents the biggest diameter borehole on land, on a stable and permeable land (preferably a rocky one) where the other two wells will be installed. Each well will be interconnected to one of the three membrane channels.

[0038] Specifically, the borehole (4) directly connects the feed flow to the channel 1 of the membrane as the arrows indicate.

[0039] Mark 5It represents the well of the concentrate with an ascending flow. As the arrows indicate in the drawing, the dynamic level is slightly lower than the borehole level because of being interconnected through the channel 2, after the flow has gone trough the membrane spiral.

[0040] Mark 6It represents the well of the permeate, which is connected thorough the channel 3 of the membrane, in which it is deposited (drained) without pressure inside the well, which is closed at the bottom. It forms this way a permeate collection container, which is connected through the top to the surface in order to achieve a correct suction.

[0041] Mark 7It represents the symbol of the submerged motor pump in the well (5) of the concentrate, which is in charge from the suction to the outlet. Its functioning causes a level drop inside the borehole that forces the flow, through channel 1, thorough the membrane using the principle of the communicating vessels.

[0042] Mark 8It represents the symbol of the submerged motor pump in the well (6) of the permeate, which is in charge from the water product extraction to the surface, overtaking the load due to the depth.

[0043] Mark 9It represents the membrane packet which is installed inside a tube in which the direction of the three flows can be seen.

[0044] FIG. 3It shows a cross-section view of the floating platform with the anchors and two headframes from which two wells (14) are articulately hanging (well of the concentrate+well of the permeate) at a depth of 450 m.

[0045] Around each well (14), at the bottom, the membrane packet (15) can be found with the corresponding connexions to each well (see the below enlarged detail).

[0046] At the bottom of each of the two wells of the permeate there is the motor pump (8) of the permeate extraction that is inverted-mounted in order to produce the permeate water extraction thorough two hosepipes (16) which pass along the sea bed to the coast for the use thereof.

PREFERRED EMBODIMENT OF THE INVENTION

[0047] The objective of the present descriptive memory is to describe the method and means for diluting or concentrating solutions applied to processes for the desalination of water, that is to say, to obtain the production of fresh water from seawater or salty water by means of a reverse osmosis method with a lower energy demand and a lower environmental impact.

[0048] It involves obtaining the maximum permeate flow possible for the minimum energy cost by using the reverse osmosis method.

[0049] It is here searched a better quality of 350 ppm, at year zero with water at 22? C. and a salinity in the entrance flow of 32.000 ppm.

[0050] The well is created in 30 days, reaching the static level of the water at 4 m, which happens to meet the ground level. Rocky and stable lands are gone through, and in the first 10 m of the borehole the diameter has increased to 680 mm and the lands were then piped and cemented. The distance to the coast was 80 m.

[0051] During the development of the well by means of over-pumping with the suction of a motor pump located at 440 m, 300 m3/h were reached pumping during 24 hours with a level drop stabilised at 1.7 m, which gives credit to a good transmission. The water came up in a clear form and without turbidity at a temperature of 22? C. During the last 24 hours some samples were taken for testing every two hours. Once the equipment is dismantled, it is checked with an interior diameter that there were no landslides. The interior diameter of 650 mm goes through the bottom.

[0052] Once the hydraulic performance of the well is known and once the flow-drop curve is established, along with the data of the physicochemical and biological analysis is of the water, the membrane packet (9) is projected with the program: LG NANO H2O QA+V2.3 until searching for the number and the type of membrane that guarantees the required quality and quantities.

[0053] From 8-inches membranes, having 24 tubes in four levels of six tubes per level and 5 membranes, a LGSW440ES tube-type, we will compose a membrane packet (9) that takes up a diameter that fits snug inside the borehole.

[0054] It can be seen that if we have 6 tubes with 5 membranes that are grouped around a central tube (brine manifold) of a 219 mm diameter, these would be fitted in a 635 mm diameter, leaving a space of ?12.5 mm that it is considered to be adequate.

[0055] With this same provision, three other groups will be placed in order to achieve the four levels of 6?5?4=120 membranes.

[0056] The obtained hydraulic data during the well (4) development, the analysis and the temperatures, they were introduced in the program Q+projection software of NanoH2O, of which a summary of the presented data is attached, which is sorted by channels.

[0057] Feed Flow (Channel 1) (Provided Via the Borehole)

RO Feed flow 231 m3/h

Stage 1

Vessels 24

Elements 5

[0058] Number of elements 120
ERD type: one

Feed TDS 31.999 ppm

Osmotic Pressure Feed 22.92 bar

Temp 22? C.

[0059] Feed Pressure 44.35 bar (provided via the well suggestion)

[0060] Concentrate Flow (Channel 2)

Concentrate flow 148 m3/h (provided via the suction of the motor pump (7) of the well of the concentrate well (5))

Recovery 64.07%

Osmotic Pressure Concentrate 35.69 bar

[0061] Drop Pressure 1.2 bar (lost through the 5-membranes tube)

[0062] Permeate Flow (Channel 3)

Permeate flow 83 m3/h (provided via the motor pump (8) of the well (6) of the permeate, which is hollow and at atmospheric pressure)

Recovery 35.93%

Permeate TUS 221 ppm

[0063] It is planned this way to group together 6 five-membrane tubes in series which are connected to the concentrate common manifold through channel 2 (brine) on a first level, and a second group of the same characteristics on a second level. A third group would be on a third level and finally a forth group would be on a forth level, making a total of 24 five-membrane tubes, which would have permeate manifolds (channel 3) that converge the well (6) of the permeate which is located at the bottom of the borehole (4).

[0064] The brine pump (7) should pump 65% of the feed raw water causing a dynamic level drop that compensates the loading losses caused by the flow transport of raw water thorough the well (4) (downward direction), apart from the loss of a membrane packet (9), and the load loss of the ascending flow of the brine, inside the well (5), to the pump (7) which will carry it until pouring it to the outlet.

[0065] This load loss will be seen when comparing the difference among the dynamic levels between the borehole (4) and the well (5) of the brine.

[0066] By calculating an average transport speed of 0.3 m/s in the ring section that is between the borehole (4) and the largest diameter piping, the load loss will be 3 mca, in addition to the dynamic level drop which was measured in the well (4) development phase that will be around 1.7 mca. This means that the total load loss caused by the feed raw water flow will be 4.7 mca.

[0067] The load loss obtained in the membrane packet (9) (feed pressure?concentrate pressure) obtained by the NanoH2O is 1.2 bar.

[0068] Equally, the load loss in the piping of the well of the brine (ascending flow) for a transport speed of 0.9 m/s all the way to the pump (7) will be 2.5 mca.

[0069] These losses add up 4.7+12.4+2.5=19.6 mca.

[0070] The pump suction level required by the brine motor pump (7) (4 m) to determine its installation minimum depth must be added to the slope:

19.6+4=23.6 m.

[0071] 30 m are adopted as the installation depth of the brine motor pump (7).

[0072] In order to select the motor pump (7), this load (19.6) will have to be taken into account. To this load, the load caused at the 30 m of the pressure pipe (10) till the outlet (1.5 m) will be added. This way the height the motor pump will have to overcome will be 21.1 m, the flow to be pumped being 65% of the feed one, that is, 0.65?231=150m3/h, the required power being 18 kW.

[0073] As membranes are developed to permeate at atmospheric pressure or at very low pressure (?1 bar), it will be necessary to connect the permeate (channel 3) with an area being at a pressure similar to the atmospheric one.

[0074] In order to achieve this objective, a tube that will act as an air vent will be connected to the bottom of the well (6) so that it could be at atmospheric pressure.

[0075] Inside this well (6), at the bottom, a motor pump (8) being able to extract to the surface the whole volume of permeate water should be installed.

[0076] The permeate flow will be 36% of the feed corresponding one, that is: 0.36?231=83.16 m3/h.; taking into account that the permeate vessel is located at a depth of 440 m.

[0077] Therefore, the power required by the osmosis method will be 18.5+132=150.5 kW that are necessary to obtain 83.16 m3/h of permeate water, with a specific power ratio of 150.5/83.16=1.809 kw/m3.

[0078] The maximum dimensions in diameter of the motor pumps determine the minimum diameter of the two wells to be installed inside the borehole.

[0079] However, the well (5) of the brine (concentrate) works at low differential pressure between the interior and exterior walls. Therefore, it is not subject to big loads in spite of the depth, excepting its own weight and the osmosis equipment weight.

[0080] However, the well (6) of the permeate, in addition to the described loads, because of being hollow and at atmospheric pressure as it is submerged at 440 m, it is subject to an external pressure that can make it collapse. Therefore, its thickness and material resistance should be duplex stainless steel with an elastic limit of 450 N/mm2 calculated from a ?=p*r/t=44*30/0.6=2200 Kg/cm2, complying with the minimum thickness of 6 mm, in diameter 0.6 m.

[0081] The thickness that should be adopted for the two parallel pipes that will physically form both wells (5 and 6) that will be installed inside the borehole (4) at a depth of 450 m is of 3 mm in duplex quality, this is to say, the two wells (permeate (6) and concentrate (5)) will be duplex pipes (270?3) connected by one double flange in lengths of 12 m. The total equipment weight is then, including the osmosis plant, 23 Tm of dry weight and 20 Tm when it is submerged in the well inside de water.

[0082] Another alternative would be arranging the concentric pipes sharing the flanges that will have ports available in order to give distance and continuity.

[0083] The portico and the winch that are used for its assembly will be measured so that they can raise 25 Tonnes.

[0084] These calculations, sizes and method are good for the case when both wells (brine (5) permeate (6)) would have to work on the sea bed hanging from a floating platform (11), and being installed in both wells (14) and the membrane packet (9) hanging from two headframes (13) were assembled by means of drive shaft joint.

[0085] The floating platform (11) is anchored to the sea bed with cables (12) that affix it to fixed moorings on the sea bed.

[0086] The permeate motor pump (8) works in an inverted position in order to propel the permeate water through two hosepipes (16) that carry the water through the sea bed to the coast for the use thereof.

[0087] In the unlikely event of the borehole (4) being drilled on an impermeable ground, producing a dry well near the sea, the wellhead will be connected to the coast through a packet of gravel filters in order to supply the borehole (4) with seawater. This way, the osmosis method could be carried out following the principles and characteristics patented here.

[0088] The nature and details of the present invention being sufficiently described, as well as the way to put it into practice, making a more extensive explanation is not considered so that any expert in the art could understand the importance and advantages that derive from it. It is placed on the record that, within the specialization, the invention could be implemented in other ways that differ in detail to the one described here, as an example, and to which the requested protection will equally apply, provided that its fundamental principle is not altered, changed or modified.

[0089] Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the allowed claims and their legal equivalents.