Desalination plant for salt water, comprising a device for switching supply and discharge pipes, and associated implementation method

Abstract

The invention relates to a desalination plant (10) for salt water (11), comprising: - a membrane filtration unit (12), - a first pipe assembly (14) and a second pipe assembly (16) which are fluidically connected to the membrane filtration unit (12). The desalination plant (10) further comprises a device (18) for reversibly switching said plant (10) between a first configuration in which the pipe (30) of the first assembly (14) is a supply pipe for the plant (10) and the pipe (32) of the second assembly (16) is a discharge pipe for the plant, and a second configuration in which the pipe (30) of the first assembly (14) is the discharge pipe and the pipe (32) of the second assembly (16) is the supply pipe.

Description

A saline water desalination plant comprising a device for switching between the supply and discharge pipes, and the associated implementation method.

[0001] The present invention relates to a saline water desalination plant.

[0002] In particular, the invention relates to an installation comprising a membrane filtration unit, in particular by reverse osmosis, configured to desalinate saline water, in particular seawater or brackish water from a body of water, and provide a concentrate flow and a permeate flow.

[0003] This type of installation generally includes one or more supply lines for pumping salt water, and one or more discharge lines for the flow of permeate and brine into the sea.

[0004] Supply pipelines are generally located away from the coast to capture better quality seawater and avoid coastal contaminants.

[0005] The discharge pipes are placed at a certain distance from the coast, away from the supply pipes and at a suitable depth to promote the dilution and dispersion of the brine over a wide area, thus reducing the impact on the marine ecosystem.

[0006] Biofouling, also known as "biological fouling" in English, is a common and problematic phenomenon in feed pipes. It involves the accumulation and growth of microorganisms and marine animals, such as shellfish, crustaceans or sponges, on the submerged surfaces of feed pipes, particularly at suction openings and inside the pipe.

[0007] Biological fouling reduces the effective diameter of the pipe and increases the roughness of its inner surface, decreasing the flow of saline water to the system. This results in pressure losses and consequently increased energy consumption for pumping water.

[0008] Biological fouling therefore requires regular cleaning and maintenance operations which further increase the operating costs of the installation.

[0009] For example, it is known to use a scraper piston type device to scrape the inside of the pipe along its entire length in order to eliminate marine life that has colonized the inner wall of the pipe.

[0010] Scraping can also be carried out using a remote-controlled scraping device or manually by sending divers into the pipe.

[0011] These techniques are lengthy, costly, and require extended plant shutdowns. Furthermore, they can also lead to the movement of a significant amount of organic matter and shells into the plant, which must be blocked at the inlet, for example, by installing screens, and then removed. This also results in substantial operating costs.

[0012] Another technique for eliminating biofouling involves injecting chemicals to limit the growth of marine life inside the pipe. However, marine life adapts to these chemicals, rendering this technique ineffective. Furthermore, chemical injection can negatively impact the lifespan of the equipment, particularly the durability of reverse osmosis membranes. Finally, this technique is expensive due to the significant chemical consumption.

[0013] One aim of the invention is to provide a saline water desalination plant which significantly reduces the impact of biological fouling on the saline water supply pipes while limiting the impact on the plant's production and operating costs.

[0014] To this end, the invention relates to a saline water desalination plant comprising:

[0015] - a membrane filtration unit configured to desalinate saline water from a body of water and provide a concentrate flow and a permeate flow,

[0016] - a first set of pipe(s) comprising at least one pipe and a second set of pipe(s) comprising at least one pipe, the pipes of each of the first and second sets being fluidically connected to the membrane filtration unit and each comprising a free termination intended to be in fluidic communication with the body of water, the free terminations of each of the pipes of each of the first and second sets being distinct from each other,

[0017] in which the desalination plant further comprises a reversible switching device for said plant between a first configuration in which the pipe or each pipe of the first set is a supply pipe of the plant configured to supply the membrane filtration unit with saline water from the free termination of the pipe or each pipe of the first set, and the pipe or each pipe of the second set is a discharge pipe of the plant configured to discharge the concentrate flow into the body of water through the free termination of the pipe or each pipe of the second set,and a second configuration in which the pipe or pipes of the first set are a discharge pipe configured to discharge the concentrate stream into the body of water through the free termination of the pipe or pipes of the first set, and the pipe or pipes of the second set are a supply pipe configured to supply the membrane filtration unit with saline water from the free termination of the pipe or pipes of the second set.

[0018] Thus, periodically switching the supply and discharge pipes allows the flow of concentrate, i.e., brine, to circulate through the pipe(s) that were previously used to supply the system with saline water. The high salinity of the brine acts as a growth inhibitor and even a biocide on the marine life that contributes to the biological fouling. Furthermore, circulating the concentrate helps to flush dead marine organisms or those whose adhesion has been weakened out of the pipe.

[0019] The installation according to the invention may comprise one or more of the following features, taken individually or in any technically possible combination:

[0020] - the first set of driving(s) includes at least two driving(s) and the second set of driving(s) includes at least two driving(s);

[0021] - the free termination of each delimiting pipe delimits a plurality of through openings spaced apart from each other along a main direction of pipe elongation, each through opening being configured to allow an entry of saline water into the pipe or a discharge of the concentrate flow out of the pipe;

[0022] - the free termination includes a free end, the free end delimiting a transverse opening extending in a plane substantially perpendicular to the main direction of elongation, the transverse opening being intended to put the interior of the pipe into fluidic communication with a volume of saline water;

[0023] - the membrane filtration unit comprises a saline water inlet fluidly connected to the first set of pipe(s) and a concentrate flow outlet fluidly connected to the second set of pipe(s), the switching device comprising at least one first set of taps including at least one tapping pipe fluidly connecting the concentrate flow outlet to the first set of pipe(s) and a second set of taps including at least one tapping pipe fluidly connecting the saline water inlet to the second set of pipe(s); and

[0024] - The switching device also includes:

[0025] * at least one first reversibly movable switching element between a first position in which said first switching element permits the passage of a fluid between the salt water inlet and the first set of pipe(s) and does not permit the passage of a fluid between the salt water inlet and the second set of branch(s), and a second position in which said first switching element does not permit the passage of a fluid between the water inlet and the first set of pipe(s) and permits the passage of a fluid between the salt water inlet and the second set of branch(s);

[0026] * at least one second switching member is reversibly movable between a first position in which said second switching member permits the passage of a fluid between the concentrate outlet and the second set of pipe(s) and does not permit the passage of a fluid between the concentrate outlet and the first set of branch(s), and a second position in which said second switching member does not permit the passage of a fluid between the concentrate outlet and the second set of pipe(s) and permits the passage of a fluid between the concentrate outlet and the first set of branch(s).

[0027] The invention also relates to a method for implementing a desalination plant as described above, comprising the following steps:

[0028] - a first stage of operation of the installation in the first configuration for an initial period, the first set of pipe(s) forming the saline water supply pipe(s) to the membrane filtration unit, the saline water supply being carried out from the free termination of the pipe(s) of the first set, the second set of pipe(s) forming the concentrate flow discharge pipe(s) into the body of water, the concentrate flow being discharged from the free termination of the pipe(s) of the second set,

[0029] - a second stage of operation of the installation in the second configuration for a second duration, the first set of pipe(s) forming the pipe(s) for the discharge of the concentrate flow into the body of water, the discharge of the concentrate flow being carried out by the free termination of the pipe(s) of the first set, the second set of pipe(s) forming the pipe(s) for the supply of saline water, the supply of saline water being carried out from the free termination of the pipe(s) of the second set.

[0030] The method according to the invention may comprise one or more of the following features, taken individually or in any technically feasible combination:

[0031] - the first and second durations are between 3 days and 60 days;

[0032] - the first stage and the second stage form a sequence, a production duration of the installation comprising a plurality of consecutive sequences;

[0033] - from one sequence to another consecutive sequence, the first duration and the second duration differ from each other;

[0034] - In the first configuration, the filtration unit is supplied with saline water from a first region of the water body, the concentrate flow being discharged into a second region of the water body, separate from the first region, and in the second configuration, the filtration unit is supplied with saline water from the second region of the water body, the concentrate flow being discharged into the first region of the water body; and

[0035] - the membrane filtration unit includes a salt water inlet, the membrane filtration unit being supplied by said inlet in the first configuration and in the second configuration.

[0036] The invention will be better understood upon reading the following description, given solely by way of example, and made with reference to the attached drawings, among which: a is a schematic view of an installation according to the invention in the first configuration; a is a schematic view of an installation according to the invention in the second configuration; and a is a schematic view of one end of a supply / discharge pipe of an installation according to an embodiment.

[0037] Figures 1 and 2 schematically illustrate a desalination installation 10 of saline water 11 according to the invention.

[0038] The installation 10 includes a membrane filtration unit 12, a first set 14 of pipe(s), a second set 16 of pipe(s) and a switching device 18 between a first configuration of the installation () and a second configuration of the installation ().

[0039] The membrane filtration unit 12 is preferably a reverse osmosis membrane filtration unit known from the prior art. The membrane filtration unit 12 comprises, in a known manner, a plurality of reverse osmosis modules (not shown) arranged in a rack configured to filter saline water 11 and produce a permeate stream 20, i.e. desalinated water, and a concentrate stream 22, i.e. brine.

[0040] The membrane filtration unit 12 includes a saline water inlet 24, a concentrate outlet 26 and a permeate outlet 28.

[0041] The principle of reverse osmosis is known from the prior art and is not detailed in this description.

[0042] The body of water is, for example, a sea, an ocean, or a body of brackish water.

[0043] Salt water is, for example, seawater or brackish water.

[0044] Salt water 11 has a salinity greater than 1 g / L, for example between 10 g / L and 40 g / L for seawater, preferably greater than 30 g / L.

[0045] The permeate flux 28 typically exhibits a salinity of less than 0.1 g / L.

[0046] The concentrate stream 26 has a high salinity, between 2 g / L and 80 g / L, for example between 20 g / L and 80 g / L for seawater, preferably greater than 60 g / L.

[0047] The installation 10 generally includes a pretreatment unit (not shown) fluidically connected to the membrane filtration unit 12, upstream of said unit 12, intended to pretreat the saline water 11 supplying the installation 10. In particular, the pretreatment unit makes it possible to remove debris and solid particles present in the saline water 11, to reduce organic matter and control the chemical properties and to protect the membranes of the membrane filtration unit 12.

[0048] The first set of 14 driving(s) includes at least one 30 driving.

[0049] The second set 16 of driving(s) includes at least one driving 32.

[0050] In the example of figures 1 and 2, the first set 14 of conduct(s) includes a single conduct 30. Similarly, the second set 16 of conduct(s) includes a single conduct 32.

[0051] Alternatively, the first set 14 of conduct(s) includes a plurality of conduct(s) 30, for example two conduct(s) 30. Similarly, the second set 16 of conduct(s) includes a plurality of conduct(s) 32, for example two conduct(s) 32.

[0052] The diameter of pipes 30 and 32 in the first set of pipes (14) and the second set of pipes (16) is adjusted according to the feed rate and concentrate discharge rate by a person skilled in the art. For example, the diameter is between 200 mm and 4000 mm.

[0053] Each pipe 30, 32 of each set 14, 16 of pipe(s) is fluidly connected to the installation 10 and in particular to the membrane filtration unit 12.

[0054] Each pipe 30, 32 of each set 14, 16 of pipe(s) includes a free termination intended to be in fluidic communication with the body of water. The free terminations of each of the first and second sets 14, 16 are distinct from each other.

[0055] The conduct(s) 30 of the first set 14 of conduct(s) are distinct from the conduct(s) 32 of the second set 16 of conduct(s).

[0056] According to the invention, the switching device 18 is configured to switch the installation 10 reversibly between the first configuration () and the second configuration ().

[0057] In the first configuration, the pipe(s) 30 of the first set 14 of pipe(s) is / are a supply pipe(s) of the installation 10 configured to supply the filtration unit 12 with saline water 11 from the body of water from the free termination 46 of the pipe(s) 30 of the first set 14. The pipe(s) 32 of the second set 16 of pipe(s) is / are a discharge pipe of the installation 10 configured to discharge the concentrate flow 22 produced by the installation 10 into the body of water from the free termination 46 of the pipe(s) 32 of the second set 16.

[0058] In the second configuration, the pipe(s) 30 of the first set 14 of pipe(s) is / are the discharge pipe(s) and the pipe(s) 32 of the second set 16 of pipe(s) is / are the supply pipe(s).

[0059] In other words, in the first configuration, the filtration unit 11 is supplied with saline water from a first region of the water body. The concentrate flow 22 is discharged into a second region of the water body, separate from the first region.

[0060] In the second configuration, the filtration unit is supplied with saline water from the second region of the water body. The concentrate stream 22 is discharged into the first region of the water body.

[0061] The free termination 46 of each of the pipes 30 of the first set 14 of pipe(s) is located in the first region of the body of water, in the first configuration and in the second configuration.

[0062] The free termination 46 of each of the pipes 32 of the second set 16 of pipe(s) is located in the second region of the body of water, in the first configuration and in the second configuration.

[0063] The second region is located away from the first region, preferably in areas of the body of water that allow good dispersion of the concentrate flow 22.

[0064] The membrane filtration unit 12 is supplied by the saline water inlet 24 in both the first and second configurations. In other words, the membrane filtration unit 12 has a single saline water inlet 24, identical in both the first and second configurations.

[0065] In the embodiment shown in Figures 1 and 2, the switching device 18 comprises a first set 34 of branch connections including at least one branch line 36 fluidly connecting the concentrate outlet 26 to the first set 14 of branch lines. The switching device 18 further comprises a second set 38 of branch connections including at least one branch line 40 fluidly connecting the saline water inlet 24 to the second set 16 of branch lines.

[0066] In the example shown in Figures 1 and 2, the first set of branch connections 34 comprises a single branch line 36 fluidly connecting the concentrate outlet 26 to the single line 30 of the first set of lines 14. The second set of branch connections 38 comprises a single branch line 40 fluidly connecting the single line 32 of the second set of lines 16 to the salt water inlet 24.

[0067] For example, as illustrated in Figures 1 and 2, the permutation device 18 comprises a first permutation member 42 and a second permutation member 44.

[0068] The first switching member 42 is reversibly movable between a first position in which said first switching member 42 permits the passage of a fluid between the salt water inlet 24 and the first set 14 of pipe(s) and does not permit the passage of a fluid between the salt water inlet 24 and the second set 38 of branch(s), and a second position in which said first switching member 42 does not permit the passage of a fluid between the water inlet 24 and the first set 14 of pipe(s) and permits the passage of a fluid between the salt water inlet 24 and the second set 38 of branch(s).

[0069] The second switching member 44 is reversibly movable between a first position in which said second switching member 44 permits the passage of a fluid between the concentrate outlet 26 and the second set 16 of pipe(s) and does not permit the passage of a fluid between the concentrate outlet 26 and the first set 34 of branch(s), and a second position in which said second switching member 44 does not permit the passage of a fluid between the concentrate outlet 26 and the second set 16 of pipe(s) and permits the passage of a fluid between the concentrate outlet 26 and the first set 34 of branch(s).

[0070] In the first configuration of the installation 10 (), the first switching element 42 and the second switching element 44 are each in their first position.

[0071] In the second configuration of the installation 10 (), the first switching element 42 and the second switching element 44 are each in their second position.

[0072] For example, the first switching organ 42 and the second switching organ 44 are formed by three-way valves.

[0073] Figure 1 illustrates an embodiment of a termination 46 of a pipe 30, 32 of the first set 14 of pipe(s) and the second set 16 of pipe(s) intended to be immersed in a body of saline water to be desalinated. The termination 46 of the pipe 30, 32 extends along a principal elongation direction L and delimits a plurality of through openings 48 establishing fluidic communication between the interior of the pipe 30, 32 and the saline water 11. The through openings 48 are arranged along the principal elongation direction L. Their number and diameter are chosen by those skilled in the art according to the saline water supply flow rate of the installation 10, the number of pipes 30, 32, the concentrate flow rate, and environmental constraints.

[0074] For example, a larger dimension of the through opening 48 is greater than 100 mm.

[0075] The number of through openings 48 is, for example, between 1 and 12.

[0076] Advantageously, the end 50 of the termination 46 defines a transverse opening 49 extending in a plane substantially perpendicular to the main direction L putting the interior of the conduit 30, 32 into fluidic communication with the expanse of saline water.

[0077] The transverse opening 49 makes it easier to expel dead marine organisms or those whose adhesion has been weakened from the conduit.

[0078] Advantageously, the termination 46 includes at least a diameter reduction 52 from a portion directed towards the membrane filtration unit 12 towards the end 50 of the termination 46. This allows the flow velocity to be increased at the end 49 of the termination 46, further facilitating the expulsion of marine organisms.

[0079] A method for implementing a saline water desalination installation 10 according to the invention will now be described.

[0080] The installation 10 is initially implemented in the first configuration for an initial period. The first set 14 of pipe(s) then forms the saline water supply pipe(s) 11 to the membrane filtration unit 12. The second set 16 of pipe(s) forms the concentrate flow discharge pipe(s) 22.

[0081] The initial duration, for example, ranges from 3 to 60 days. This allows the brine to act as a growth inhibitor or even a biocide on the marine life that makes up the biological fouling.

[0082] Then, the configuration of installation 10 is reversed, and installation 10 is operated in the second configuration for a second period. The first set 14 of pipe(s) then forms the discharge pipe(s) for the concentrate stream 22. The second set 16 of pipe(s) forms the saline supply pipe(s) for the membrane filtration unit 12.

[0083] The second duration, for example, is between 3 and 60 days.

[0084] Installation 10 operates according to a cycle, sometimes in the first configuration, sometimes in the second configuration during a production time of installation 10. The cycle includes a plurality of consecutive sequences, each sequence including operation in the first configuration for a first duration and operation in the second configuration for a second duration.

[0085] Advantageously, from one sequence to the next, the first and second durations differ from each other to prevent marine life from adapting to the brine. In other words, the operating cycle between the first and second configurations is irregular.

[0086] Thus, the high salinity concentrate 22 flow sometimes through pipe(s) 30 of the first set 14 of pipe(s) and sometimes through pipe(s) 32 of the second set 16 of pipe(s) allowing to limit the growth or even destroy the biological fouling present in pipes 30, 32.

Claims

Installation (10) for desalinating saline water (11) comprising: - a membrane filtration unit (12) configured to desalinate saline water (11) from a body of water and provide a concentrate flow (22) and a permeate flow (20), - a first set (14) of pipe(s) comprising at least one pipe (30) and a second set (16) of pipe(s) comprising at least one pipe (32), the pipes (30, 32) of each of the first and second sets (14, 16) being fluidically connected to the membrane filtration unit (12) and each comprising a free termination (46) intended to be in fluidic communication with the body of water, the free terminations (46) of each of the pipes (30, 32) of each of the first and second sets (14, 16) being distinct from each other,characterized in that the desalination plant (10) further comprises a reversible switching device (18) of said plant (10) between a first configuration in which the pipe or each pipe (30) of the first assembly (14) is a supply pipe of the plant (10) configured to supply the membrane filtration unit (12) with saline water (11) from the free termination (46) of the pipe or each pipe (30) of the first assembly (14), and the pipe or each pipe (32) of the second assembly (16) is a discharge pipe of the plant (10) configured to discharge the concentrate flow (22) into the body of water through the free termination (46) of the pipe or each pipe (32) of the second assembly (16),and a second configuration in which the pipe or each pipe (30) of the first assembly (14) is a discharge pipe configured to discharge the concentrate stream (22) into the body of water through the free termination (46) of the pipe or each pipe (32) of the first assembly (14) and the pipe or each pipe (32) of the second assembly (16) is a supply pipe configured to supply the membrane filtration unit (12) with saline water (11) from the free termination (46) of the pipe or each pipe of the second assembly (16). Desalination installation (10) according to claim 1 wherein the first set (14) of pipe(s) comprises at least two pipe(s) (30) and the second set (16) of pipe(s) comprises at least two pipe(s) (32). Desalination installation (10) according to claim 1 or 2, wherein the free termination (46) of each pipe (30, 32) delimits a plurality of through openings (48) spaced from one another along a principal elongation direction (L) of the pipe (30, 32), each through opening (48) being configured to permit an inflow of saline water (11) into the pipe (30, 32) or a discharge of the concentrate flow (22) out of the pipe (30, 32). Desalination installation (10) according to claim 3, wherein the free termination (46) comprises a free end (50), the free end (50) defining a transverse opening (49) extending in a plane substantially perpendicular to the principal direction of elongation (L), the transverse opening (49) being intended to put the interior of the pipe (30, 32) into fluidic communication with a volume of saline water. Installation (10) according to any one of claims 1 to 4, wherein the membrane filtration unit (12) comprises a saline water inlet (24) fluidly connected to the first set (14) of pipe(s) and a concentrate flow outlet (26) fluidly connected to the second set (16) of pipe(s), the switching device (18) comprising at least a first set of tap(s) (34) comprising at least one tapping pipe (36) fluidly connecting the concentrate flow outlet (26) to the first set (14) of pipe(s) and a second set (38) of tap(s) comprising at least one tapping pipe (40) fluidly connecting the saline water inlet (24) to the second set (16) of pipe(s). Installation (10) according to claim 5, wherein the switching device (18) further comprises: - at least one first switching member (42) reversibly movable between a first position in which said first switching member (42) permits the passage of a fluid between the salt water inlet (24) and the first set (14) of pipe(s) and does not permit the passage of a fluid between the salt water inlet (24) and the second set (38) of branch(s), and a second position in which said first switching member (42) does not permit the passage of a fluid between the water inlet (24) and the first set (14) of pipe and permits the passage of a fluid between the salt water inlet (24) and the second set (38) of branch(s),- at least one second switching member (44) is reversibly movable between a first position in which said second switching member (44) allows the passage of a fluid between the concentrate outlet (26) and the second set (16) of pipe(s) and does not allow the passage of a fluid between the concentrate outlet (26) and the first set (34) of branch(s), and a second position in which said second switching member (44) does not allow the passage of a fluid between the concentrate outlet (26) and the second set (16) of pipe(s) and allows the passage of a fluid between the concentrate outlet (26) and the first set (34) of branch(s). A method for implementing a saline water desalination plant (10) according to any one of claims 1 to 6, comprising the following steps: - a first step of operating the plant (10) in the first configuration for a first duration, the first set (14) of pipe(s) forming the saline water supply pipe(s) (11) to the membrane filtration unit (12), the saline water supply (11) being carried out from the free termination (46) of the pipe(s) (30) of the first set (14), the second set (16) of pipe(s) forming the concentrate flow discharge pipe(s) (22) into the body of water, the concentrate flow (22) being discharged from the free termination (46) of the pipe(s) (32) of the second set (16), - a second step of operating the plant (10) in the second configuration for a second duration,the first set (14) of pipe(s) forming the discharge pipe(s) of the concentrate stream (22) into the body of water, the discharge of the concentrate stream (22) being effected by the free termination (46) of the pipe(s) (30) of the first set (14), the second set (16) of pipe(s) forming the salt water supply pipe(s) (11), the salt water supply (11) being effected from the free termination (46) of the pipe(s) (32) of the second set (16). A method according to claim 7, wherein the first duration and the second duration are between 3 days and 60 days. Method according to claim 7 or 8, wherein the first step and the second step form a sequence, a production duration of the installation (10) comprising a plurality of consecutive sequences. A method according to claim 9, wherein, from one sequence to another consecutive sequence, the first duration and the second duration differ from each other. A method according to any one of claims 7 to 10, wherein, in the first configuration, the filtration unit (11) is supplied with saline water from a first region of the water body, the concentrate flow (22) being discharged into a second region of the water body, separate from the first region, and in the second configuration, the filtration unit (11) is supplied with saline water from the second region of the water body, the concentrate flow (22) being discharged into the first region of the water body. A method according to any one of claims 7 to 11, wherein the membrane filtration unit (12) comprises a salt water inlet (24), the membrane filtration unit (12) being supplied by said inlet (24) in the first configuration and in the second configuration.

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