System for reverse osmosis

Abstract

The invention relates to a system for multi-stage reverse osmosis (RO), the system comprising: a first RO stage (10) having a first feed inlet (11), a first brine outlet (12) and a first permeate outlet (13); a second RO stage (20) having a second feed inlet (21), a second brine outlet (22) and a second permeate outlet (23); and a pressure exchanger PE (40) connected between the second brine outlet (22) and the first feed inlet (11), wherein a first pressure difference Δp1 between the first brine outlet (12) and the second feed inlet (21) corresponds to a second pressure difference Δp2 between the second brine outlet (22) and the pressure exchanger (40). The invention allows to shut down the second stage of the RO system in order to adapt to external circumstances such as fluctuations in energy price and / or brine concentration. The invention also relates to a method for operating such a reverse osmosis system (100).

Description

Technical Field

[0001] This invention relates to systems for reverse osmosis, and more particularly to multi-stage reverse osmosis systems with improved energy efficiency. The invention also relates to methods for operating such systems, exemplarily used for producing fresh water. The invention allows for adaptation to different energy prices and / or dissolved salt concentrations. Background Technology

[0002] Osmosis is the process by which solvent moves across a semipermeable membrane from the membrane side facing a lower solute concentration to the membrane side facing a higher solute concentration. The movement of solvent particles is driven by diffusion, and overall, more solvent particles diffuse towards the higher solute concentration (i.e., the lower water potential energy), resulting in a net movement of solvent. This naturally occurring process is also the basis of the reverse osmosis process, as described below.

[0003] In reverse osmosis, pressure exceeding the osmotic pressure is applied to the side with the higher solute concentration, thereby restoring the energy balance of the osmosis system. This results in a net overall diffusion movement across the membrane from the high solute concentration to the low solute concentration, thus increasing the solute concentration on the pressurized membrane side. A reverse osmosis system includes at least two chambers separated by a semi-permeable membrane, wherein the inflow and outflow of the chambers can be controlled to set volumetric flow conditions and a pressure gradient across the membrane.

[0004] Reverse osmosis (RO) is frequently used in water purification or desalination applications, where it produces highly concentrated brine alongside purified water and / or demineralized water. The brine is retained on the pressurized side of the membrane, while the purified water and / or demineralized water (permeate) is removed from the other membrane side at low pressure. The pressurized brine is removed from the reverse osmosis chamber to avoid an excessive increase in osmotic pressure and to allow fresh feed solution to flow into the chamber. Energy recovery devices (e.g., hydraulic turbines) are also known for transferring hydraulic energy from the pressurized brine to the feed solution to improve the overall energy efficiency of the reverse osmosis process.

[0005] It is also known to combine multiple RO stages in such systems to improve energy efficiency and freshwater production. In such multi-stage RO systems, RO chambers are typically combined in a linear fashion. The brine is usually pressurized before entering subsequent stages to compensate for the increased solute concentration. Hydraulic turbines are also used in multi-stage RO systems for energy recovery and efficiency enhancement.

[0006] The use of turbines typically requires the conversion of hydraulic energy into mechanical energy, and then into electrical energy, on the motor side for energy transfer. On the pump side, this conversion then needs to be reversed, from electrical energy to mechanical energy, and then further to hydraulic energy. This generally reduces the overall energy efficiency of the RO system. Pressure exchangers, which allow direct energy transfer between fluid flows, avoid such conversion losses but have a rather narrow window for optimal transfer efficiency, which is often not met in RO systems.

[0007] EP 4 342 573 A1 discloses an advantageous multi-stage RO system in which the brine outlet of the first RO stage is further pressurized by another pressure pump and fed into the second RO stage. The principle can be extended accordingly by adding additional stages.

[0008] However, a limitation of RO systems according to EP 4 342 573 A1 is that all brine from the outlet of one stage needs to completely flow into the next stage, thus connecting the membrane crossflow between the two stages. To do this, all brine from the outlet of (e.g.) the first stage typically needs to be further pressurized, as the pressure in subsequent stages is usually significantly higher than in the previous stage due to the higher solute concentration. While all attempts aim to recover as much energy as possible, it is sometimes desirable to reduce energy consumption, especially when energy prices do increase. Furthermore, adaptation to different brine concentrations, different water temperatures, varying degrees of wear on components in the RO system, and even different membrane types is desired.

[0009] Therefore, the purpose of this disclosure is to overcome or at least reduce the disadvantages of the prior art and to provide a multi-stage system for reverse osmosis with adaptable energy efficiency. Summary of the Invention

[0010] The purpose of this disclosure is achieved and the disadvantages of the prior art are overcome or at least reduced by the subject matter of this invention, namely by the system for reverse osmosis (RO) according to the appended claims and by the method for operating such a system. Current multi-stage RO systems are characterized by quick connections between subsequent stages, which allows the system to be better adapted to external factors such as energy prices, freshwater demand, brine concentration, and crossflow requirements.

[0011] A first aspect of this disclosure relates to a system for reverse osmosis (RO), the system comprising a first RO stage having a first feed inlet, a first brine outlet, and a first permeate outlet. The first RO stage includes a first high-pressure RO chamber and a first low-pressure RO chamber separated by a first RO membrane. These chambers preferably form an RO tank configured to accommodate the first RO process and withstand the pressures that arise. The first RO stage may include more inlets and / or outlets, such as multiple first feed inlets, multiple first brine outlets, and / or multiple first permeate outlets. For brevity, only one of these inlets and outlets will be referred to below. In a first RO stage including multiple inlets and / or outlets, the following interpretation may refer to the relationship between individual inlets and / or outlets, and / or the relationship between multiple inlets and / or outlets. Such a system has been disclosed in EP 4 342 573 A1.

[0012] At least one first feed inlet is configured to supply a feed solution stream to a first high-pressure RO chamber, and at least one first brine outlet is configured to discharge a brine solution from said chamber. A first low-pressure RO chamber is configured to receive permeate, i.e., a feed solution with a reduced solute concentration, via a first RO membrane. At least one first permeate outlet is configured to discharge permeate from the first low-pressure RO chamber. The upwardly concentrated feed solution (brine) is discharged via at least one first brine outlet at a pressure substantially the same as the pressure of the feed solution at at least one first feed inlet. Permeate is discharged via at least one first permeate outlet at a pressure significantly lower than the feed pressure (preferably as low as possible to achieve an optimal pressure differential at the membrane).

[0013] The first RO membrane is configured to allow the solvent of the feed solution to diffuse under external pressure applied to the first high-pressure RO chamber. In a preferred embodiment, the feed solution is brine, such as seawater, and the first RO membrane is configured to allow water to diffuse through the membrane while preventing salt ions (e.g., Na+) from diffusing through it. + and Cl - The first RO membrane is preferably configured to prevent organic matter, bacteria, and pyrogens from passing through it; however, these components may have been removed in a pretreatment stage prior to the RO chamber. The first RO membrane is preferably one of a cellulose acetate (CA) membrane or a polysulfone membrane, which may be coated with an aromatic polyamide. Also preferred are nanostructured, zeolite, and / or spiral-wound RO membranes.

[0014] The RO system disclosed herein also includes a second RO stage having a second feed inlet, a second brine outlet, and a second permeate outlet. The second RO stage includes a second high-pressure RO chamber and a second low-pressure RO chamber separated by a second RO membrane. These chambers preferably form a second RO tank configured to accommodate the second RO process and withstand the pressures that arise. The second RO stage may include more inlets and / or outlets, such as multiple second feed inlets, multiple second brine outlets, and / or multiple second permeate outlets. For brevity, only one of such inlets and outlets will be referred to below. In a second RO stage including multiple inlets and / or outlets, the following interpretation may refer to the relationship between individual inlets and / or outlets, and / or the relationship between multiple inlets and / or outlets.

[0015] At least one second feed inlet is configured to supply a feed solution stream to a second high-pressure RO chamber, and at least one second brine outlet is configured to discharge a brine solution from the second chamber. The feed solution fed to the at least one second feed inlet is at least partially a brine solution discharged from the at least one first brine outlet. A second low-pressure RO chamber is configured to receive permeate via a second RO membrane. At least one second permeate outlet is configured to discharge permeate from the second low-pressure RO chamber. Permeate from the first and second low-pressure chambers may be discharged jointly. Sometimes, the two permeate outlets remain separate. Sometimes, only one type of permeate has a sufficiently low salt content to be potable. Sometimes, the second stage is configured to desalinate only the feed to the salinity level of the first feed inlet. The second permeate outlet can then be connected to the inlet side of the first high-pressure pump.

[0016] Similarly, in the second RO stage, brine is discharged via at least one second brine outlet at a pressure substantially the same as that of the feed solution (first-stage brine) at at least one second feed inlet, while permeate is discharged via at least one second permeate outlet at a lower pressure, preferably significantly lower than the feed pressure, or even as low as possible. The second RO membrane is configured in the same or similar manner as the first RO membrane.

[0017] The system disclosed herein also includes a pressure exchanger PE connected between a second brine outlet and a first feed inlet. In other words, the pressure exchanger includes: an inlet (particularly a high-pressure HP inlet) configured to receive a brine stream discharged from the second brine outlet; and an outlet (particularly a high-pressure HP outlet) configured to supply a feed solution stream to the first feed inlet. The pressure exchanger also includes: another outlet (particularly a low-pressure LP outlet) configured to discharge a depressurized brine stream; and another inlet (particularly a low-pressure LP inlet) configured to receive a feed solution stream to be pressurized.

[0018] In the system of this disclosure, the first pressure difference Δp1 between the first brine outlet and the second feed inlet corresponds to the second pressure difference Δp2 between the second brine outlet and the pressure exchanger. In other words, the first pressure difference Δp1 relates to the pressure difference between the pressure of the brine solution discharged via the first brine outlet and the pressure of the feed solution entering the second RO stage via the second feed inlet. The feed solution entering the second RO stage via the second feed inlet is at least partially, and preferably entirely, derived from the brine solution discharged via the first brine outlet. Therefore, the first pressure difference Δp1 and the second pressure difference Δp2 are not independent of each other, but rather correspond to each other, because the first pressure difference Δp1 is set to a value dependent on the value of the second pressure difference Δp2, or the second pressure difference Δp2 is set to a value dependent on the value of the first pressure difference Δp1.

[0019] Specifically, the system of this disclosure includes: a first device for generating a first pressure difference, the first device being disposed between a first brine outlet and a second feed inlet; and a second device for generating a second pressure difference, the second device being disposed between a second brine outlet and a pressure exchanger. The system of this disclosure also includes a control unit for controlling the first device for generating the first pressure difference and the second device for generating the second pressure difference. The control unit is configured to control the first device and the second device to set the first pressure difference and the second pressure difference correspondingly to each other. Specifically, the control unit is configured to set the value of the first pressure difference Δp1 based on the value of the second pressure difference Δp2, or to set the value of the second pressure difference Δp2 based on the value of the first pressure difference Δp1. More preferably, the control unit is configured to control the first pressure difference and the second pressure difference such that the first pressure difference and the second pressure difference automatically adjust relative to each other, thereby matching the first pressure difference and the second pressure difference.

[0020] When the first device is preferably one of a hydraulic pump and a hydraulic motor, and then the second device is preferably the other of a hydraulic pump and a hydraulic motor. Each of the first and second devices may also be one of a high-pressure pump, an interstage booster pump, a turbine, and an isobaric pressure exchanger connected to a high-pressure booster pump (preferably implemented with a Danfoss iSave pump, which provides a combination of an isobaric pressure exchanger connected to a high-pressure booster pump), as long as the above correspondence can be ensured.

[0021] Therefore, the system of this disclosure is operable in which the pressure difference between the first brine outlet and the second feed inlet changes by a first pressure difference Δp1, and the pressure difference between the second brine outlet and the pressure exchanger changes by a second pressure difference Δp2 corresponding to the first pressure difference Δp1, and wherein hydraulic energy is thus advantageously transferred with increased efficiency via the pressure exchanger from the second brine stream flowing from the second brine outlet to the first feed stream supplied to the first feed inlet. Increased efficiency can be achieved through the pressure configuration of the disclosed system (i.e., the corresponding first and second pressure differences), which allows the pressure exchanger to operate with optimal transfer efficiency. According to this disclosure, the first pressure difference Δp1 and / or the second pressure difference Δp2 can have positive or negative pressure values.

[0022] According to a preferred embodiment of the RO system, the pressure exchanger PE has a high-pressure HP inlet connected to a second brine outlet and a PE HP outlet connected to a first feed inlet, and a second pressure difference Δp2 occurs between the second brine outlet and the PE HP inlet. Therefore, in the RO system of this disclosure, a second pressure difference Δp2 is generated before the brine stream is fed into the pressure exchanger, so as to feed the brine stream into the pressure exchanger at an optimized pressure. In this way, the efficiency of hydraulic energy transfer in the pressure exchanger, which is configured to pressurize the feed stream supplied to the first feed inlet, is advantageously improved. Also advantageously, in this embodiment, the booster pump is located upstream of the second brine outlet.

[0023] Further preferably, in the system of this disclosure, a first pressure difference Δp1 is utilized to generate a second pressure difference Δp2. In other words, hydraulic energy associated with the first pressure difference Δp1 is captured and used to generate the second pressure difference Δp2. Similarly, it is preferred that the second pressure difference Δp2 is utilized to generate the first pressure difference Δp1. Likewise, this essentially refers to the transfer of hydraulic energy associated with the first pressure difference Δp1 and the second pressure difference Δp2. Wherein, generating the second pressure difference Δp2 by utilizing the first pressure difference Δp1 does not necessarily mean providing energy to generate the second pressure difference Δp2, but in the same way, the second pressure difference Δp2 can be generated by removing hydraulic energy from the system using the first pressure difference Δp1. The transfer of hydraulic energy associated with the first pressure difference Δp1 and the second pressure difference Δp2 can occur directly or indirectly by converting it into other forms of energy. Exemplarily, hydraulic energy can be converted into mechanical energy and / or electrical energy for transfer between the first pressure difference Δp1 and the second pressure difference Δp2. Preferably, the first device for generating the first pressure difference and the second device for generating the second pressure difference are connected to each other via a connection that allows energy to be transferred directly (e.g., mechanically) or indirectly (e.g., via a conversion from hydraulic energy to electrical energy and a reverse conversion from electrical energy to hydraulic energy).

[0024] In a particularly preferred embodiment of the system disclosed herein, the pressure exchanger is an isobaric pressure exchanger. More preferably, the pressure exchanger is configured to transfer pressure from a pressurized brine flow downstream of a second brine outlet to a low-pressure feed solution upstream of a first feed inlet using a positive displacement principle. In such an isobaric pressure exchanger, pressure transfer occurs from the high-pressure (brine) flow to the low-pressure (feed) flow by bringing the high-pressure (brine) flow and the low-pressure (feed) flow into direct, instantaneous contact. Such isobaric pressure exchangers are known to those skilled in the art, and earlier forms of such isobaric pressure exchangers are disclosed, for example, in US 2,675,173 B or EP 0298097A1. A modern example of an isobaric pressure exchanger is the pressure exchanger within the Danfoss iSave device.

[0025] As explained in EP 4 342 573 A1, the energy efficiency of an isobaric pressure exchanger increases when the pressure difference in the pressure exchanger decreases. In particular, the smaller the pressure difference between the high-pressure inflow and high-pressure effluent, the better the energy efficiency. Furthermore, the better the energy efficiency of an isobaric pressure exchanger, the smaller the pressure difference between the low-pressure inflow and low-pressure effluent. The system of this disclosure advantageously reduces these pressure differences.

[0026] Preferably, the pressure exchanger is a rotary pressure exchanger, and particularly preferably has a cylindrical rotor with longitudinal conduits oriented parallel to the axis of rotation, as shown in EP 4 342 573 A1.

[0027] In a particularly preferred embodiment of the system disclosed herein, a hydraulic motor is connected between the second brine outlet and the high-pressure inlet of the pressure exchanger. More preferably, the hydraulic motor is an axial piston motor including a mechanical shaft connected to a swashplate carrying a plurality of pistons arranged inside a cylinder, or directly connected to such a cylinder, as disclosed in EP 4 342573 A1.

[0028] In this preferred embodiment, the pressure at the first brine outlet is preferably less than the pressure at the second feed inlet. Exemplarily, the first RO stage operates at a high pressure level of approximately 60 bar, while the second RO stage operates at a high pressure level of approximately 120 bar. Since the pressure difference in the high-pressure RO chamber is negligible, the pressure at the first brine outlet is approximately 60 bar, while the pressure at the second feed inlet is approximately 120 bar. Therefore, the first pressure difference Δp1 here is a pressure rise, and thus the second pressure difference Δp2 is a pressure drop. Particularly preferably, a hydraulic pump is interconnected between the first brine outlet and the second feed inlet to provide the pressure rise of the first pressure difference Δp1 to the brine flow upstream of the second feed inlet. More preferably, the hydraulic pump between the first brine outlet and the second feed inlet is (at least partially) powered by a hydraulic motor that provides the pressure drop of the second pressure difference Δp2 downstream of the second brine outlet upstream of the pressure exchanger.

[0029] In another particularly preferred embodiment, a hydraulic pump is connected between the second brine outlet and the high-pressure inlet of the pressure exchanger. The hydraulic pump is preferably an axial piston pump comprising a mechanical shaft connected to a swashplate carrying a plurality of pistons arranged inside a cylinder, or directly connected to such a cylinder, as disclosed in EP 4 342 573 A1.

[0030] In this preferred embodiment, the pressure at the first brine outlet is preferably greater than the pressure at the second feed inlet. Exemplarily, the first RO stage operates at a high pressure level of approximately 120 bar, while the second RO stage operates at a high pressure level of approximately 60 bar. Since the pressure difference in the high-pressure RO chamber is negligible, the pressure at the first brine outlet is approximately 120 bar, while the pressure at the second feed inlet is approximately 60 bar. Therefore, the first pressure difference Δp1 here is a pressure drop, and the second pressure difference Δp2 is a pressure rise. Preferably, a hydraulic motor is connected between the first brine outlet and the second feed inlet to provide the pressure drop as the first pressure difference Δp1. More preferably, the hydraulic motor between the first brine outlet and the second feed inlet (at least partially) powers a hydraulic pump, thereby providing the pressure rise of the second pressure difference Δp2 upstream of the pressure exchanger.

[0031] In the system of this disclosure and in each of the embodiments described above, the first pressure difference Δp1 is preferably greater than 5 bar, preferably greater than 10 bar, more preferably greater than 15 bar, particularly preferably greater than 20 bar, even more preferably greater than 30 bar, preferably greater than 40 bar, and even more preferably greater than 50 bar. In other words, the first RO stage and the second RO stage preferably operate at high pressure levels that are different from each other (“far apart”). In the system of this disclosure, the difference in high pressure levels is represented by the first pressure difference Δp1, which corresponds to the second pressure difference Δp2 introduced upstream of the pressure exchanger. By coupling the first pressure difference Δp1 and the second pressure difference Δp2, the energy efficiency of the system is improved by manipulating the pressure levels of the pressure exchanger without requiring external energy. Therefore, the system of this disclosure can be advantageously used if there is a considerably high or variable difference in the high pressure levels of a multi-stage RO system. A particularly advantageous coupling method will now be described in more detail.

[0032] Preferably, in the system of this disclosure, the first pressure difference Δp1 is approximately 70% to 130% of the second pressure difference Δp2; more preferably, the first pressure difference Δp1 is approximately 80% to 120% of the second pressure difference Δp2; even more preferably, the first pressure difference Δp1 is approximately 90% to 110% of the second pressure difference Δp2; and particularly preferably, the first pressure difference Δp1 is approximately 95% to 105% of the second pressure difference Δp2. It is particularly preferred that the first pressure difference Δp1 has an equal amount to the second pressure difference Δp2, as some pressure loss occurs in the high-pressure RO chambers of the first and second RO stages, fluid conduits, and other parts of the RO system. Therefore, equal amounts of the first pressure difference Δp1 and the second pressure difference Δp2 may not be maintained in all operating states of the system. Preferably, the control unit controls the first device for generating the first pressure difference and the second device for generating the second pressure difference, thereby achieving the aforementioned correspondence between the first and second pressure differences.

[0033] However, neither the first pressure difference Δp1 nor the second pressure difference Δp2 can be constant. Pressure losses occur in any multi-stage RO system, within the RO chamber, PE unit, and / or piping. While efforts are made to keep these losses as low as possible, it is impossible to intentionally set (i.e., strictly control) the relationship between the first pressure difference Δp1 and the second pressure difference Δp2; these pressure differences are a result of system design and the flow rate through the system. However, in the system of this disclosure, any change in pressure losses, such as due to increased flow rate, membrane aging, etc., causes the first pressure difference Δp1 and / or the second pressure difference Δp2 to automatically adjust relative to each other, matching them. Therefore, in cases where pressure needs to be increased in an additional booster with external energy, the pressure at the HP inlet of the pressure exchanger always matches the HP outlet pressure. Thus, the system of this disclosure advantageously provides a very flexible solution that can easily handle changes in flow rate or pressure within the system without any loss of efficiency.

[0034] In a preferred embodiment of the system disclosed herein, a hydraulic motor interconnected between the first brine outlet and the second feed inlet, or one of the second brine outlets, and the PE HP inlet, and a hydraulic pump interconnected between the other of the first brine outlet and the second feed inlet, or the other of the second brine outlets, and the PE HP inlet, are mechanically connected to each other. This embodiment advantageously allows energy to be transferred directly from the hydraulic motor to the hydraulic pump without any conversion losses, particularly without any losses due to the conversion of mechanical energy to electrical energy and vice versa. A preferred embodiment of the hydraulic motor is disclosed in EP 4 342 573 A1.

[0035] In such an embodiment, the hydraulic energy supplied by the hydraulic pump and / or consumed by the hydraulic motor can be adapted to match each other, thereby allowing a trouble-free direct mechanical connection. Exemplarily, the pressure drop at the hydraulic motor can be adjusted (e.g., reduced) to match (e.g., reduced) the hydraulic energy converted into mechanical energy there. Similarly, the pressure rise at the hydraulic pump can be adjusted (e.g., increased) to match the mechanical energy supplied via a common shaft. An adjustable valve can be used to perform this adaptation. Thus, the aforementioned components can realize a connection configured to allow energy transfer between a first and a second device for generating a pressure difference.

[0036] More preferably, the mechanical connection is an indirect mechanical connection, for example, via a gearbox, transmission, and / or clutch. In such an embodiment, preferably, the output shaft of the hydraulic motor is mechanically connected to the input shaft of the hydraulic pump via a gearbox, transmission, and / or clutch, as explained in detail in EP 4 342 573 A1. Therefore, the aforementioned components can realize a connection configured to allow energy transfer between a first and a second device for generating a pressure difference.

[0037] Those skilled in the art will recognize various designs of such induction motors, which are commonly used in a variety of industrial applications, such as, for example, wind turbines. Exemplary designs, schematic diagrams, and circuit diagrams are disclosed, for example, in S. Müller; S. et al. (2002), “Doubly Fed Induction Generator Systems for Wind Turbines” (PDF); IEEE Journal of Industrial Applications; IEEE.8(3):26-33; doi:10.1109 / 2943.999610, and in Roberts, Paul C. (2004), “Study of Brushless Doubly-Fed (Induction) Machines; Contributions in Machine Analysis, Design and Control” (PDF); Emmanuel College, University of Cambridge. The entire contents of the above documents are incorporated herein by reference.

[0038] According to this preferred embodiment, the rotor of the induction motor is mechanically connected to the input shaft of the hydraulic pump and also mechanically connected to the output shaft of the hydraulic motor. In other words, also in this embodiment, there is an indirect mechanical connection between the hydraulic pump and the hydraulic motor. In the context of this application, input / output shaft refers to any mechanical component (e.g., a pinion gear) configured to transmit mechanical energy input / output by a given device. The mechanical connection between the rotor and the hydraulic motor and / or hydraulic pump is a direct mechanical connection (e.g., via the common shaft of the induction motor) or an indirect mechanical connection (e.g., via a gearbox). Particularly preferably, the induction motor is a dual-shaft induction motor or a double-shaft induction motor, wherein the rotor is connected to two shafts, one of which is then preferably connected to the hydraulic motor and the other to the hydraulic pump. In the system according to this embodiment, the hydraulic pump and the hydraulic motor are mechanically connected via the rotor of the induction motor. This again allows energy to be transferred directly from the hydraulic motor to the hydraulic pump without conversion losses, particularly without losses due to power conversion in power converters (such as, for example, AC / DC, AC / AC, or DC / DC converters or frequency converters). Therefore, the above-mentioned components can be configured as a connection that allows energy transfer between a first device and a second device for generating a pressure difference.

[0039] Furthermore, the combination of the hydraulic motor, induction motor, and hydraulic pump can be (configured) to operate with net positive power production, wherein the generated power can be advantageously distributed and / or used to operate other electrical equipment in the system, such as a feed pump. Moreover, the system configuration allows for easy compensation of the energy difference between the hydraulic motor and the hydraulic pump by adding or drawing power from the system. Preferably, the induction motor is capable of operating with variable slip, wherein positive slip corresponds to an operating mode in which the induction motor consumes energy, for example, to compensate for pressure loss, and wherein negative slip corresponds to an operating mode in which the induction motor generates electrical energy, i.e., in which the induction motor acts as a generator. Therefore, the aforementioned components can realize a connection configured to allow energy transfer between the first and second devices used to generate the pressure difference.

[0040] Compared to the RO system described in EP 4 342 573 A1, the current system includes a fluid connection between the pipeline connecting the first brine outlet to the second hydraulic pump and the pipeline connecting the hydraulic motor to the high-pressure inlet of the pressure exchanger PE (see [link to RO system description]). Figure 2aThis additional fluid connection eliminates the need for any valves or throttle valves. The additional fluid connection creates a shortcut between the second-stage brine outlet and the first-stage brine outlet. This enables several operating modes of interest. If the system operates as described above by generating, for example, a high pressure level of approximately 60 bar at the first RO stage 10 and by generating a high pressure level of approximately 120 bar, and the setpoint of the interstage booster pump is adjusted such that it drives the same amount of flow exiting the first brine outlet through it, the result is the same as without the additional fluid connection. The second hydraulic pump pumps all the brine from the first brine outlet into the second RO chamber. However, if the second hydraulic pump and turbine are shut down, the brine from the first brine outlet flows directly into the pressure exchanger through the additional line, similar to standard single-stage RO operation. In this operating mode, the entire system consumes significantly less energy. The operating point of the interstage booster pump can also be set to pump only half the flow exiting the first-stage brine outlet. In this way, scenarios between the first two operating modes can be achieved, illustrating the operational flexibility of the invention. If the interstage booster pump is pumping more flow than is leaving the first-stage brine outlet, an alternative operating mode can be imagined. In this case, the additional flow pumped by the interstage booster pump is supplied from the second-stage brine outlet, thus recirculating the second-stage brine back into the second-stage inlet. Many other flexible operating modes exist that can be achieved by adjusting the flow rates through process-defined machines, such as high-pressure pumps, interstage booster pumps, turbines, and isobaric pressure exchangers connected to high-pressure booster pumps (preferably implemented with Danfoss iSave pumps, which provide a combination of isobaric pressure exchangers connected to high-pressure booster pumps). And when these identified machines are based on positive displacement technology, this enables ultra-precise flow control regardless of the pressures present in either stage, greatly simplifying operational control.

[0041] Based on experience, the second stage of the described RO system requires the same amount of energy as the first stage, but produces only 50% more permeate (i.e., demineralized water). In other words, by shutting down the second stage, the system produces approximately 67% more permeate using about 50% of the energy.

[0042] Those skilled in the art will understand that by using this principle, the system can be adapted to different energy prices and / or water demands: if electricity prices are low, the system can use two stages for freshwater production, while if energy prices rise, the system can shut down the second stage. Similarly, when water demand is high, the system can use both stages, while when water demand decreases, the system can use only the first stage. Finally, if the desired output is not primarily freshwater production, but rather an upward concentration of the final brine outlet, the system can be configured as described above to recirculate the brine outlet of the second stage back into the feed inlet of the second stage. This will consume more energy because the salinity level will increase in the second stage, resulting in a higher concentration level at the final brine outlet.

[0043] This adaptation to different needs is important. For example, in areas where electricity is mainly generated by solar panels: during the day, when solar supply is high and water consumption is high, the RO system can use two stages, while at night, the second stage can be turned off, which saves 50% of electricity while maintaining 67% of freshwater production.

[0044] Those skilled in the art will further understand that the system can not only be turned on or off, but can also be regulated across the entire range (0 to 100% power) to optimize the ratio of energy consumption to water production. For example, the first stage can operate with the aforementioned first pressure difference Δp1 of 60 bar, and the second stage can operate with the aforementioned second pressure difference Δp2 of, for example, 20 bar, 30 bar, or 40 bar.

[0045] Similarly, this system can be adapted to varying brine concentrations. In some areas, groundwater has fluctuating salt content. When salt content is high, the osmotic pressure of the solution is high, which in turn requires higher pressure for reverse osmosis. Because the solute concentration in the brine is much higher than that in the feed, excessive pressure is required for the second stage. In such areas, the RO system can operate with only the first stage when the feed has a high solute concentration, and activate the second stage when the solute concentration decreases.

[0046] Another aspect of this disclosure relates to a method for operating a reverse osmosis (RO) system according to this disclosure as described above. The method of this disclosure includes at least the step of: preferably changing the pressure between a first brine outlet and a second feed inlet by a first pressure difference Δp1 via a first device for generating a first pressure difference (particularly preferably one of a hydraulic motor (pressure drop) and a hydraulic pump (pressure rise)). More preferably, the first pressure difference Δp1 is at least partially or completely affected by said one of the hydraulic pump and the hydraulic motor. The method further includes the step of: preferably changing the pressure between a second brine outlet and a pressure exchanger by a second pressure difference Δp2 corresponding to the first pressure difference Δp1 via a second device for generating a second pressure difference (particularly preferably another of a hydraulic motor (pressure drop) and a hydraulic pump (pressure rise)). The second pressure difference Δp2 is preferably at least partially or completely affected by said other of the hydraulic pump and the hydraulic motor. Preferably, the above steps are performed by controlling the first and second devices for generating the pressure difference via a control unit. The method further includes the step of transferring hydraulic energy from a second brine stream exiting a second brine outlet to a first feed stream supplied to a first feed inlet via a pressure exchanger. This step is preferably performed via a connection between the first and second devices, which allows for direct or indirect transfer of (hydraulic) energy. The method disclosed herein enables such energy transfer with optimal efficiency.

[0047] In a preferred embodiment, the method disclosed herein is used to operate a system that further includes a third RO stage interconnected between the first and second RO stages, and includes a third feed inlet, a third brine outlet, and a third permeate outlet. In such an embodiment, an optional additional fluid connection is established between the line connecting the second brine outlet to the third hydraulic pump and the line connecting the hydraulic motor to the high-pressure inlet of the pressure exchanger PE.

[0048] According to this embodiment, the method further includes the following step: changing the pressure difference Δp between the first brine outlet and the third feed inlet. 3,1 And the pressure difference Δp between the third brine outlet and the second feed inlet. 3,2 Among them, the pressure difference Δp 3,1 and pressure difference Δp 3,2 The sum of these values ​​is at least equal to the first pressure difference Δp1. Furthermore, the pressure difference Δp 3,1 and pressure difference Δp 3,2 At least one pressure difference is affected by one of the hydraulic motor and the hydraulic pump, while the second pressure difference Δp2 is affected by the other of the hydraulic motor and the hydraulic pump. More preferably, if the pressure difference Δp 3,1 and pressure difference Δp3,2 If a pressure difference is affected by either a hydraulic motor or a hydraulic pump, then the pressure between the first brine outlet and the second feed inlet is considered to change the first pressure difference Δp1 via said one of the hydraulic motors and pumps. In other words, in this case, the first pressure difference Δp1 can be partially affected by either the hydraulic motor or the hydraulic pump, and partially by other devices (e.g., pressure exchangers). This applies to RO stages including even other stages (e.g., fourth RO stage, fifth RO stage, etc.) and thus introducing other pressure differences Δp1. 4,1 and Δp 4,2 , Δp 5,1 and Δp 5,2 The same applies to RO systems. Furthermore, some of these pressure differentials can be introduced by a hydraulic pump or motor and / or pressure exchanger. In this embodiment, the system preferably includes a third device for generating a third pressure differential, and the control unit is preferably configured to control the first, second, and third devices for generating the pressure differential to adjust the first, second, and third pressure differentials correspondingly to each other.

[0049] Further preferred embodiments of the method of this disclosure correspond to preferred embodiments of the system of this disclosure as described above, and provide the advantages of the system of this disclosure as described above. Other aspects and preferred embodiments of the invention are disclosed by the dependent claims, the drawings, and the following description of the drawings. Unless otherwise explicitly stated, the different disclosed embodiments are advantageously combined with each other. Attached Figure Description

[0050] The features of the invention will become clear to those skilled in the art from the detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0051] Figure 1 A system for RO according to a first embodiment is schematically illustrated;

[0052] Figure 2 , Figure 2a and Figure 2b The figure illustrates a system for RO according to a second embodiment;

[0053] Figure 3 The figure illustrates a system for RO according to a third embodiment;

[0054] Figure 4 The figure illustrates a system for RO according to a fourth embodiment;

[0055] Figure 5 and Figure 5a The figure illustrates a system for RO according to a fifth embodiment;

[0056] Figure 6 The figure illustrates a system for RO according to a sixth embodiment;

[0057] Figure 7 The illustration shows a system for RO according to a seventh embodiment; and

[0058] Figure 8 The illustration depicts a method for RO according to an embodiment. Detailed Implementation

[0059] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. The effects and features of exemplary embodiments and their implementation methods will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same elements, and redundant descriptions are omitted. The invention may be embodied in various different forms and should not be construed as being limited to the embodiments illustrated herein. These embodiments are provided as examples so that this disclosure will be complete and will fully convey various aspects and features of the invention to those skilled in the art.

[0060] Therefore, elements that are not necessary for those skilled in the art to fully understand the features of the invention may not be described.

[0061] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, the use of "may" in describing embodiments of the invention means "one or more embodiments of the invention." In the following description of embodiments of the invention, singular terms may include plural terms unless the context clearly indicates otherwise.

[0062] It should be understood that although the terms "first" and "second" are used to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be named a second element without departing from the scope of the invention, and similarly, a second element may be named a first element. As used herein, the terms "substantially," "approximately," and similar terms are used as approximate terms rather than as terms of degree, and are intended to take into account the inherent deviations of measured or calculated values ​​that will be recognized by those skilled in the art. Furthermore, if the term "substantially" is used in conjunction with a feature that can be expressed numerically, the term "substantially" indicates a range of + / -5% of the value centered on that value.

[0063] Figure 1 A system 100 for reverse osmosis (RO) according to a first embodiment is schematically illustrated, the system 100 including a first RO stage 10 and a second RO stage 20.

[0064] The first RO stage 10 includes a first feed inlet 11, a first brine outlet 12, a first permeate outlet 13, and a first high-pressure RO chamber 15 and a first low-pressure RO chamber 16, which are separated by a first RO membrane 14 and together form a first RO tank. A first feed stream 17 is fed into the first high-pressure RO chamber 15 via the first RO feed inlet 11, and a first brine stream 19 is discharged via the first brine outlet 12. Furthermore, a first permeate stream 18 is discharged from the first low-pressure RO chamber 16 via the first permeate outlet 13.

[0065] The second RO stage 20 includes a second feed inlet 21, a second brine outlet 22, a second permeate outlet 23, a second high-pressure RO chamber 25, and a second low-pressure RO chamber 26. The second high-pressure RO chamber 25 and the second low-pressure RO chamber 26 are separated by a second RO membrane 24 and together form a second RO tank. The second feed stream 27 is fed into the second high-pressure RO chamber 25 through the second RO feed inlet 21, and the second brine stream 29 is discharged through the second brine outlet 22.

[0066] A fluid connection (19a) is established between the line connecting the first brine outlet (12) to the second hydraulic pump (60) and the line connecting the hydraulic motor (50) to the high-pressure inlet (41) of the pressure exchanger PE (40). Additionally, a second permeate stream 28 is discharged from the second low-pressure RO chamber 26 via the second permeate outlet 23. Each of the inlet and outlet may be valve-controlled, where an active or passive valve (e.g., a check valve) may be used. The system also includes another liquid source (not shown) for compensating for permeate taken from the system 100 via permeate outlets 13, 23, i.e., for also adding to the first feed stream 17.

[0067] The RO system 100 also includes a pressure exchanger PE 40, particularly an isobaric and / or rotary pressure exchanger 40. The pressure exchanger 40 includes a PE high-pressure inlet 41, a PE HP outlet 42, an HP low-pressure LP inlet 43, and a PE LP outlet 44. The PE HP inlet 41 is connected to a second brine outlet 22, i.e., the PE HP inlet 41 is located downstream of the second brine outlet 22 and receives a second brine flow 29 discharged from the second brine outlet 22. The PE HP outlet 42 is connected to a first feed inlet 11 via a booster pump (51), i.e., the PE HP outlet 42 is located upstream of the first feed inlet 11 and provides a first feed flow 17 to the first feed inlet 11. Therefore, PE 40 connects the second brine outlet 22 and the first feed inlet 11.

[0068] like Figure 1As shown, the first pressure difference Δp1 between the first brine outlet 12 and the second feed inlet 21 corresponds to the second pressure difference Δp2 between the second brine outlet 22 and the pressure exchanger 40. The pressure at the first brine outlet 12 differs from the pressure at the second feed inlet 21 by the first pressure difference Δp1. Furthermore, the pressure at the second brine outlet 22 differs from the pressure at the PE / HP inlet 41 by the second pressure difference Δp2. The first pressure difference Δp1 is preferably greater than 20 bar, more preferably greater than 35 bar, and even more preferably greater than 50 bar. When the second pressure difference Δp2 corresponds to the first pressure difference Δp1, the second pressure difference Δp2 is also preferably greater than these values. The first pressure difference Δp1 can be exactly the same as the second pressure difference Δp2, but the first pressure difference Δp1 corresponds to at least about 80% to 120% of the second pressure difference Δp2, preferably about 90% to 110%, and particularly preferably about 95% to 105%.

[0069] Setting the first pressure difference Δp1 and the second pressure difference Δp2 in this corresponding manner provides an advantageous effect, namely, to operate the isobaric pressure exchanger 40 with optimal energy transfer efficiency. This is achieved by ensuring that the pressure differences (specifically, the pressure difference between the pressure levels at the PEHP inlet 41 and the PEHP outlet 42, and the pressure difference between the pressure levels at the PELP inlet 43 and the PELP outlet 44) are the same or at least nearly the same. Thus, optimal pressure conditions and therefore optimal transfer efficiency are achieved independently of the specific system pressure.

[0070] Figure 2 A system 100 for RO according to a second embodiment is schematically illustrated, wherein the same reference numerals as in the first embodiment denote the same components, and repeated descriptions of these components are omitted for brevity.

[0071] exist Figure 2 In this system, the first pressure difference Δp1 is achieved by the (second) hydraulic pump 60.2, and the second pressure difference Δp2 is achieved by the hydraulic motor 50. In other words, the first pressure difference Δp1 corresponds to a pressure increase at the second hydraulic pump 60.2, and the second pressure difference corresponds to a pressure decrease at the hydraulic motor 50. Figure 2 In the system, the hydraulic motor 50 and the second hydraulic pump 60.2 are connected to each other via a connection configured to allow energy transfer, such as... Figure 2 As illustrated by the dashed line, energy transfer via this connection can be achieved hydraulically, mechanically, and / or electrically.

[0072] Figure 2 RO system 100 and Figure 1The system differs further in that another (first) hydraulic pump 60.1 is disposed in the first feed stream 17 for pressurizing a portion of the feed stream 17. However, a portion of the feed stream 17 is diverted upstream of the first hydraulic pump 60.1 from the feed stream 17 and is supplied to the PE LP inlet 43. This portion is then pressurized in the isobaric pressure exchanger 40 and supplied to the first feed inlet 11 via the PE HP outlet 42. In this way, it can be advantageously ensured that the volumetric flow entering the PE LP inlet 43 matches the volumetric flow entering the PE HP inlet 41, which also improves the efficiency of the PE 40.

[0073] exist Figure 2 In this embodiment, the first RO stage 10 operates at a high pressure level of approximately 60 bar, and the second RO stage 20 operates at a high pressure level of approximately 120 bar. In other words, the pressure at the first feed inlet 11 and the first brine outlet 12 is approximately 60 bar, and the pressure at the second feed inlet 21 and the second brine outlet 22 is approximately 120 bar. The pressure at the second hydraulic pump 60.2 rises to approximately 60 bar, corresponding to a pressure drop at the hydraulic motor 50, transferring energy from the hydraulic motor 50 to the second hydraulic pump 60.2. The pressure of the second brine flow 29 is approximately 120 bar upstream of the hydraulic motor 50 and approximately 60 bar downstream of the hydraulic motor 50, and the pressure at the PEHP inlet 41 is approximately 60 bar, which is approximately the same as the pressure at the first feed inlet 11 and the PEHP outlet 42.

[0074] The feed solution can be supplied at a pressure of 2 bar by the feed solution reservoir. This 2 bar pressure corresponds to the pressure at the PE LP inlet 43 and the pump inlet of the first hydraulic pump 60.1. The pressure at the PE LP outlet 44 also corresponds to 2 bar, and the pressure at the motor outlet of the first hydraulic pump 60.1 is approximately 60 bar. Therefore, in Figure 2 In the system, the pressure level for operating the pressure exchanger 40 with optimal transmission efficiency is ensured. Furthermore, the hydraulic energy removed from the system 100 via the hydraulic motor 50 to ensure these pressure levels is reintroduced into the system 100 via the second hydraulic pump 60.2 to increase the pressure for the second RO stage 20.

[0075] According to the present invention, the second stage of the RO system can be shut down by turning off the hydraulic motor 50 and the second hydraulic pump 60.2. In this operating mode, brine from the first brine outlet flows through the fluid connection 19a to the PE 40 via the inlet 41.

[0076] Figure 2a The illustration shows, for example Figure 2The system in which there is no mechanical connection between the hydraulic motor 50 and the second hydraulic pump 60.2 that would facilitate system control. The system may have an electrical connection between the hydraulic motor 50 and the second hydraulic pump 60.2.

[0077] Figure 2b The illustration shows the relationship with Figure 2 A similar alternative embodiment system, wherein the booster pump 51 is located directly before the high-pressure inlet 41 of the isobaric pressure exchanger 40.

[0078] Figure 3 A system 100 for RO according to a third embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity.

[0079] Figure 3 System 100 and Figure 2 The difference between the two systems is that the first RO stage 10 operates at a high pressure level of approximately 120 bar, while the second RO stage 20 operates at a high pressure level of approximately 60 bar. In other words, the pressure at the first feed inlet 11 and the first brine outlet 12 is approximately 120 bar, and the pressure at the second feed inlet 21 and the second brine outlet 22 is approximately 60 bar. Figure 3 The system and Figure 2 The system differs further in that the hydraulic motor 50 is positioned between the first RO stage 10 and the second RO stage 20, while the second hydraulic pump 60.2 is positioned downstream of the second brine outlet 22. Therefore, in Figure 3 In system 100, a pressure drop of approximately 60 bar is introduced between the first brine outlet 12 and the second feed inlet 21 via hydraulic motor 50, which corresponds to a pressure rise of approximately 60 bar at the second hydraulic pump 60.2. Therefore, the pressure of the second brine flow 29 is approximately 60 bar upstream of the second hydraulic pump 60.2 and approximately 120 bar downstream of the second hydraulic pump 60.2, and thus the pressure at the PE HP inlet 41 is approximately 120 bar, which is approximately the same as the pressure at the first feed inlet 11 and the PE HP outlet 42.

[0080] Similarly, the feed solution can be supplied at a pressure of 2 bar by the feed solution reservoir, which corresponds to the pressure at the PELP inlet 43 and the pump inlet of the first hydraulic pump 60.1. The pressure at the PELP outlet 44 also corresponds to 2 bar, and the pressure at the motor outlet of the first hydraulic pump 60.1 is approximately 120 bar here. Therefore, also Figure 3The system ensures the pressure level for operating the pressure exchanger 40 with optimal transmission efficiency, and the hydraulic energy removed from the system 100 via the hydraulic motor 50 is reintroduced into the system 100 via the second hydraulic pump 60.2 to increase the pressure of the second brine flow 29 upstream of the isobaric pressure exchanger 40.

[0081] Similar to the embodiments described above, the second stage of the RO system can be shut down by turning off the hydraulic motor 50 and the second hydraulic pump 60.2. In this operating mode, brine from the first brine outlet flows through the fluid connection 19a to the PE 40 via the inlet 41.

[0082] Figure 4 A system 100 for RO according to a fourth embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity.

[0083] Figure 4 System 100 and Figure 3 The difference in this system lies in that the connection between the hydraulic motor 50 and the second hydraulic pump 60.2 is achieved via an induction motor 70. The induction motor 70 can be an asynchronous motor with a stator and a rotor. The second hydraulic pump 60.2 can be an axial piston pump, and the hydraulic motor 50 can be an axial piston motor. The rotor of the induction motor 70 can be mechanically connected to the input shaft of the axial piston pump 60.2 and the output shaft of the axial piston motor 50. The rotor of the induction motor 70 can be connected to the motor shaft of the induction motor 70, which is connected to both the input and output shafts, and wherein the motor shaft can be a single continuous motor shaft or can be formed by a pair of two (dual) motor shafts.

[0084] use Figure 4 The configuration advantageously allows energy to be transferred from the hydraulic motor 50 to the second hydraulic pump 60.2 in a particularly efficient manner, i.e., without conversion losses for converting mechanical energy into electrical energy, as might occur in, for example, variable frequency drives. Furthermore, the use of an induction motor 70 for mechanically connecting the hydraulic motor 50 and the second hydraulic pump 60.2 also advantageously provides a means of efficient control of the system 100, for example, by adding the additional energy required by the second hydraulic pump 60.2 to generate a desired pressure level at the PE HP inlet 41. This can be varied by changing the slip of the induction motor 70. Additionally, at least one of the hydraulic motor 50 and the second hydraulic pump 60.2 includes a swash plate and / or mechanical gears to enable adjustment of the volume ratio and / or rotational ratio between the hydraulic motor 50 and the second hydraulic pump 60.2.

[0085] Similar to the embodiments described above, the second stage of the RO system can be shut down by turning off the hydraulic motor 50 and the second hydraulic pump 60.2. In this operating mode, brine from the first brine outlet flows through the fluid connection 19a to the PE 40 via the inlet 41.

[0086] Figure 5 A system 100 for RO according to a fifth embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity. Figure 5 System 100 has the same characteristics as the reference. Figure 2 The hydraulic motor 50 and the second hydraulic pump 60.2 described are configured identically, and are connected to each other via an induction motor 70, which provides, as referenced... Figure 4 The advantages described.

[0087] Figure 5a A system 100 for RO according to a fifth embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity. Figure 5a System 100 has the same characteristics as the reference. Figure 5 The hydraulic motor 50 described has the same configuration as the second hydraulic pump 60.2, but without the induction motor 70.

[0088] Figure 6 A system 100 for RO according to a sixth embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity.

[0089] Figure 6 The RO system 100 also includes a third RO stage 30, which includes a third feed inlet 31, a third brine outlet 32, a third permeate outlet 33, and a third high-pressure RO chamber 35 and a third low-pressure RO chamber 36. The third high-pressure RO chamber 35 and the third low-pressure RO chamber 36 are separated by a third RO membrane 34 and together form a third RO tank. A third feed stream 37 is fed into the third high-pressure RO chamber 35 via the third RO feed inlet 31, and a third brine stream 39 is discharged via the third brine outlet 32. Furthermore, a third permeate stream 38 is discharged from the third low-pressure RO chamber 36 via the third permeate outlet 33. The permeates from all three RO stages 10, 20, and 30 can be supplied jointly or individually to subsequent stages or uses.

[0090] exist Figure 6In the three-stage system, fluid connection 19a and optional second fluid connection 29a are implemented, thereby allowing the second stage and / or the third stage to be shut off independently in the same manner as described above, thus providing the benefits previously described in this specification.

[0091] exist Figure 6 In system 100, the first pressure difference Δp1 between the first RO stage 10 and the second RO stage 20 is equal to the pressure difference Δp between the first RO stage 10 and the third RO stage 30. 3,1 The pressure difference Δp between the third RO stage 30 and the second RO stage 20 3,2 Composition. For example, regarding... Figure 7 and Figure 8 The pressure difference Δp discussed in the embodiments 3,1 and Δp 3,2 At least one of the components is generated by either a hydraulic motor or a hydraulic pump. System 100 may also include additional RO stages between the third RO stage 30 and the second RO stage 20, for example, a fourth RO stage (not shown) between the third RO stage 30 and the second RO stage 20, and a fifth RO stage (not shown) between the fourth RO stage (not shown) and the second RO stage 20. Then, the pressure difference Δp... 3,2 This will be further divided into pressure difference Δp 4,1 and Δp 4,2 And the pressure difference Δp 4,2 This will be further divided into pressure difference Δp 5,1 and Δp 5,2 At least some of these pressure differences are generated by either a hydraulic motor or a hydraulic pump. Similarly, system 100 includes another liquid source (not shown) for compensating for permeate taken from system 100 via permeate outlets 13, 23, 33, i.e., for also adding to the first feed stream 17.

[0092] Figure 7 A system 100 for RO according to a seventh embodiment is schematically illustrated. The same reference numerals as in the previous embodiments denote the same components, and repeated descriptions of these components are omitted for brevity.

[0093] Figure 7 The embodiments correspond to Figure 6 In one embodiment, the pressure difference Δp 3,1 and Δp 3,2Each of these stages is generated by a hydraulic pump, specifically by a first hydraulic pump 60.1 and a second hydraulic pump 60.2. Exemplarily, the first RO stage 10 operates at a high pressure level of 60 bar, the third RO stage 30 operates at a high pressure level of 90 bar, and the second RO stage 20 operates at a high pressure level of 120 bar. In other words, the pressure at the first feed inlet 11 and the first brine outlet 12 is approximately 60 bar, the pressure at the third feed inlet 31 and the third brine outlet 32 ​​is approximately 90 bar, and the pressure at the second feed inlet 21 and the second brine outlet 22 is approximately 120 bar. Therefore, the pressure rise at the first hydraulic pump 60.1 is approximately 30 bar, and the pressure rise at the second hydraulic pump 60.2 is also approximately 30 bar. The sum of these pressure rises (i.e., 60 bar) corresponds to a pressure drop at the hydraulic motor 50. The pressure of the second brine stream 29 is approximately 120 bar upstream of the hydraulic motor 50 and approximately 60 bar downstream of the hydraulic motor 50, and therefore the pressure at the PE HP inlet 41 is approximately 60 bar, which is approximately the same as the pressure at the first feed inlet 11 and the PE HP outlet 42. Similarly, the system 100 includes another liquid source (not shown) for compensating for permeate taken from the system 100 via permeate outlets 13, 23, 33, i.e., for also adding to the first feed stream 17.

[0094] Figure 8 The illustration schematically depicts an operation as previously described in the embodiment. Figures 1 to 8 A block diagram of a method for a reverse osmosis (RO) system 100 is described. The method includes step S100: preferably via one of a hydraulic motor 50 and a hydraulic pump 60, changing a first pressure difference Δp1 between a first brine outlet 12 and a second feed inlet 21. The method further includes step S200: preferably via the other of the hydraulic motor 50 and the hydraulic pump 60, changing the pressure between a second brine outlet 22 and a pressure exchanger 40, changing a second pressure difference Δp2 corresponding to the first pressure difference Δp1. The method further includes step S300: via the pressure exchanger 40, transferring hydraulic energy from a second brine stream 28 flowing from the second brine outlet 22 to a first feed stream 17 supplied to the first feed inlet 11. This method allows a multi-stage RO system 100 with at least two RO stages 10, 20 to operate with improved energy efficiency by utilizing hydraulic energy generated by a pressure drop at a hydraulic motor 50 to generate a pressure rise at a hydraulic pump 60 and feeding a stream into a pressure exchanger 40, the pressure of which is optimized by the pressure drop or the pressure rise to improve transfer efficiency. Figure Labels 10 First RO Class 11 First feed inlet 12 First brine outlet 13 First Permeate Outlet 14 First RO Membrane 15 First High-Pressure RO Chamber 16 First Low-Pressure RO Chamber 17 First Feed Flow 18 First Penetration Logistics 19 First Saltwater Flow 19a First fluid connection part 20 Second RO Level 21 Second feed inlet 22 Second brine outlet 23 Second Permeate Outlet 24 Second RO membrane 25 Second High Pressure RO Chamber 26 Second Low-Pressure RO Chamber 27 Second feed flow 28 Second-stage logistics penetration 29 Second saline flow 29a Second fluid connection (optional) 30 Third RO level 31 Third feed inlet 32 Third brine outlet 33 Third Permeate Outlet 34 Third RO Membrane 35 Third High Pressure RO Chamber 36 Third Low-Pressure RO Chamber 37 Third feed flow 38 Third-Party Penetration Logistics 39 Third saline flow 40 (First) (Isobaric) Pressure Exchanger 41 (First) PE HP Entry 42 (First) PE HP Exports 43 (First) PE LP Entry 44 (First) PE LP Exports 45 (Second) (Isobaric) Pressure Exchanger 46 (Second) PE HP entrance 47 (Second) PE HP Exports 48 (Second) PE LP Entry 49 (Second) PE LP Exports 50 Hydraulic motor (turbine) 51 Booster Pump 60 hydraulic pump 70 Induction Motor 100 Systems for Reverse Osmosis

Claims

1. A system (100) for reverse osmosis, comprising: The first reverse osmosis stage (10) has a first feed inlet (11), a first brine outlet (12) and a first permeate outlet (13). At least a second reverse osmosis stage (20), the second reverse osmosis stage (20) having a second feed inlet (21), a second brine outlet (22) and a second permeate outlet (23); An isobaric pressure exchanger PE (40) is connected between the second brine outlet (22) and the first feed inlet (11); A hydraulic pump (60.2) and a hydraulic motor (50) are provided, wherein the hydraulic pump (60.2) is connected between the first brine outlet (12) and the second feed inlet (21), and the hydraulic motor (50) is connected between the second brine outlet (22) and the isobaric pressure exchanger (40). The booster pump (51) is connected between the high-pressure outlet (42) and the feed inlet (11) of the isobaric pressure exchanger (42), or the booster pump (51) is directly connected before the high-pressure inlet (41) of the isobaric pressure exchanger (40), and A first fluid connection (19a) is established between the first brine outlet (19) and the high-pressure inlet (41) of the hydraulic pump (50) and the pressure exchanger PE (40).

2. The system (100) according to claim 1, wherein, The isobaric pressure exchanger (40) includes a PE high-pressure HP inlet (41) connected to the second brine outlet (22) and a PE HP outlet (42) connected to the first feed inlet (11) via a booster pump (51), wherein the hydraulic motor (50) is connected between the second brine outlet (22) and the PE HP inlet (41).

3. The system (100) according to any one of the preceding claims, wherein, The isobaric pressure exchanger (40) is a rotary pressure exchanger.

4. The system (100) according to claim 2, wherein, A hydraulic motor (50) is connected between the second brine outlet (22) and the PE HP inlet (41), and wherein the pressure drop occurring at the hydraulic motor (50) is a second pressure difference Δp2 corresponding to the first pressure difference Δp1.

5. The system (100) according to claim 4, wherein, The hydraulic pump (60.2) is configured to cause the first pressure difference Δp1 such that the pressure at the first brine outlet (12) is less than the pressure at the second feed inlet (21).

6. The system (100) according to any one of claims 2 to 3, wherein, A hydraulic pump (60) is connected between the second brine outlet (22) and the PE HP inlet (41), and wherein the pressure rise occurring at the hydraulic pump (60) is a second pressure difference Δp2 corresponding to the first pressure difference Δp1.

7. The system (100) according to claim 6, wherein, The hydraulic motor (50) is configured to cause the first pressure difference Δp1 such that the pressure at the first brine outlet (12) is greater than the pressure at the second feed inlet (21).

8. The system (100) according to claim 4 or 6, wherein, One of the hydraulic motor (50), the booster pump (51), and the hydraulic pump (60) is configured to cause the first pressure difference Δp1 such that the first pressure difference Δp1 is greater than 10 bar, preferably greater than 20 bar, and even more preferably greater than 50 bar.

9. The system (100) according to claim 4 or 6, wherein, The first pressure difference Δp1 occurring at one of the hydraulic motor (50) and the hydraulic pump (60) is about 90% to 110% of the second pressure difference Δp2 occurring at the other of the hydraulic motor (50) and the hydraulic pump (60), and preferably, the first pressure difference Δp1 is about 95% to 105% of the second pressure difference Δp2.

10. The system (100) according to at least one of the preceding claims further includes a third reverse osmosis stage (30), said third reverse osmosis stage (30) being interconnected between the first reverse osmosis stage (10) and the second reverse osmosis stage (20), and having a third feed inlet (31), a third brine outlet (32) and a third permeate outlet (33), wherein, One of a second hydraulic motor and another hydraulic pump is connected between the first brine outlet (12) and the third feed inlet (31), and the first pressure difference Δp1 includes the pressure difference Δp that occurs at one of the second hydraulic motor and the other hydraulic pump between the first brine outlet (12) and the third feed inlet (31). 3,1 Furthermore, the other of the other hydraulic motor and the other hydraulic pump is connected between the third brine outlet (32) and the second feed inlet (21), and the first pressure difference Δp1 also includes the pressure difference Δp between the third brine outlet (32) and the second feed inlet (21) occurring at the other of the other hydraulic motor and the other hydraulic pump. 3,2 ; An optional additional fluid connection (29a) is established between the pipeline connecting the second brine outlet (39) to the third hydraulic pump (60.2) and the pipeline connecting the hydraulic motor (50) to the high-pressure inlet (41) of the pressure exchanger PE (40).

11. A method of operating a system (10) for reverse osmosis, the system (10) comprising: A first reverse osmosis stage (10) having a first feed inlet (11), a first brine outlet (12) and a first permeate outlet (13); A second reverse osmosis stage (20) having a second feed inlet (21), a second brine outlet (22), and a second permeate outlet (23); and an isobaric pressure exchanger (40) connected between the second brine outlet (22) and the first feed inlet (11); a hydraulic pump (60.2) connected between the first brine outlet (12) and the second feed inlet (21); and another hydraulic pump motor (50) connected between the second brine outlet (22) and the isobaric pressure exchanger (40). A booster pump (51) is connected between the high-pressure outlet (42) of the isobaric pressure exchanger (42) and the feed inlet (11), or the booster pump (51) is directly connected before the high-pressure inlet (41) of the isobaric pressure exchanger (40), and a first fluid connection (19a) is established between the first brine outlet (19) and the pipeline connecting the hydraulic pump (50) and the high-pressure inlet (41) of the pressure exchanger PE (40). The method includes the following steps: The pressure between the first brine outlet (12) and the second feed inlet (21) is changed (S100) by means of a device for generating a first pressure difference Δp1, wherein the first pressure difference Δp1 is one of pressure increase and pressure decrease; The pressure between the second brine outlet (22) and the isobaric pressure exchanger (40) is changed (S200) by means of a device for generating a second pressure difference Δp2, the second pressure difference Δp2 being the other of a pressure rise and a pressure fall, and the second pressure difference Δp2 being approximately 80% to 120% of the first pressure difference Δp1; as well as Hydraulic energy is transferred (S300) from the second brine stream (28) flowing out from the second brine outlet (22) to the first feed stream (17) provided to the first feed inlet (11) via the equal pressure exchanger (40).

12. The method for an operating system (100) according to claim 11, wherein the system (100) further comprises a third reverse osmosis stage (30) interconnected between the first reverse osmosis stage (10) and the second reverse osmosis stage (20), and the third reverse osmosis stage (30) has a third feed inlet (31), a third brine outlet (32) and a third permeate outlet (33), the method further comprising the following steps: The pressure difference Δp between the first brine outlet (12) and the third feed inlet (31) is changed. 3,1 ; The pressure difference Δp between the third brine outlet (32) and the second feed inlet (21) is changed. 3,2 ; Among them, the pressure difference Δp 3,1 With pressure difference Δp 3,2 The sum is equal to at least the first pressure difference Δp1, and Among them, the pressure difference Δp 3,1 and pressure difference Δp 3,2 At least one of the hydraulic motor (50) and the hydraulic pump (60) is affected, and the pressure difference Δp2 is affected by the other of the hydraulic motor (50) and the hydraulic pump (60).

13. A method of operating a system (10) for reverse osmosis, said system (10) comprising: A first reverse osmosis stage (10) having a first feed inlet (11), a first brine outlet (12), and a first permeate outlet (13); at least a second reverse osmosis stage (20) having a second feed inlet (21), a second brine outlet (22), and a second permeate outlet (23); an isobaric pressure exchanger PE (40) connected between the second brine outlet (22) and the first feed inlet (11); and a hydraulic pump (60) connected to the first brine outlet. Between the water outlet (12) and the second feed inlet (21); and another hydraulic pump (50) connected between the second brine outlet (22) and the isobaric pressure exchanger (40), wherein a booster pump (51) is connected between the outlet of the isobaric pressure exchanger (42) and the feed inlet (11), and wherein a first fluid connection (19a) is established between the first brine outlet (19) and the pipeline connecting the hydraulic pump (50) and the high-pressure inlet (41) of the pressure exchanger PE (40), the method comprising the steps of: The energy consumption of the reverse osmosis system is controlled by adjusting the performance of the hydraulic motor (50), booster pump (51), hydraulic pump (60.1), and hydraulic pump (60.2).

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