Abstract
A system for reverse osmosis, RO, including a first RO stage (10) with a first feed inlet (11), a first brine outlet (12), and a first permeate outlet (13); a second RO stage (20) with 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 ?p.sub.1 between the first brine outlet (12) and the second feed inlet (21) corresponds to a second pressure difference ?p.sub.2 between the second brine outlet (22) and the pressure exchanger (40). The invention further discloses a method for operating such a system for reverse osmosis (100).
Claims
1. A system for reverse osmosis, RO, comprising: a first RO stage with a first feed inlet, a first brine outlet, and a first permeate outlet; a second RO stage with a second feed inlet, a second brine outlet, and a second permeate outlet; a pressure exchanger, PE, connected between the second brine outlet and the first feed inlet, wherein a first pressure difference ?p.sub.1 between the first brine outlet and the second feed inlet corresponds to a second pressure difference ?p.sub.2 between the second brine outlet and the pressure exchanger.
2. The system according to claim 1, wherein the pressure exchanger comprises an PE HP inlet connected to the second brine outlet and an PE HP outlet connected to the first feed inlet, wherein the second pressure difference ?p.sub.2 is occurring between the second brine outlet and the PE HP inlet.
3. The system according to claim 1, wherein the first pressure difference ?p.sub.1 is utilized to create the second pressure difference ?p.sub.2 or wherein the second pressure difference ?p.sub.2 is utilized to create the first pressure difference ?p.sub.1.
4. The system according to claim 1, wherein the pressure exchanger is an isobaric pressure exchanger.
5. The system according to claim 1, wherein the pressure exchanger is a rotary pressure exchanger.
6. The system according to claim 1, wherein a hydraulic motor is connected between the second brine outlet and the PE HP inlet and wherein the pressure drop occurring at the hydraulic motor is the second pressure difference ?p.sub.2 that is corresponding to the first pressure difference ?p.sub.1.
7. The system according to claim 6, wherein a pressure at the first brine outlet is smaller than a pressure at the second feed inlet and/or a hydraulic pump is interconnected between the first brine outlet and the second feed inlet.
8. The system according to claim 1, wherein a hydraulic pump is connected between the second brine outlet and the PE HP inlet and wherein the pressure rise occurring at the hydraulic pump is the second pressure difference ?p.sub.2 that is corresponding to the first pressure difference ?p.sub.1.
9. The system according to claim 8, wherein a pressure at the first brine outlet is larger than a pressure at the second feed inlet and/or wherein a hydraulic motor is interconnected between the first brine outlet and the second feed inlet.
10. The system according to claim 1, wherein the first pressure difference ?p.sub.1 is larger than 10 bar, preferably larger than 20 bar, and further preferably larger than 50 bar.
11. The system according to claim 1, wherein the first pressure difference ?p.sub.1 is about 80% to 120% of the second pressure difference ?p.sub.2, preferably the first pressure difference ?p.sub.1 is about 90% to 110% of the second pressure difference ?p.sub.2, and particularly preferred the first pressure difference ?p.sub.1 is about 95% to 105% of the second pressure difference ?p.sub.2.
12. The system according to claim 7, wherein the hydraulic motor and the hydraulic pump are mechanically connected to each other, preferably via an induction motor.
13. The system according to claim 1, further comprising a third RO stage interconnected between the first RO stage and the second RO stage and having a third feed inlet, a third brine outlet, and a third permeate outlet, wherein the first pressure difference ?p.sub.1 comprises a pressure difference ?p.sub.3,1 between the first brine outlet and the third feed inlet and a pressure difference ?p.sub.3,2 between the third brine outlet and the second feed inlet.
14. A method of operating a system for reverse osmosis, RO, comprising a first RO stage with a first feed inlet, a first brine outlet, and a first permeate outlet, a second RO stage with a second feed inlet, a second brine outlet, and a second permeate outlet, and a pressure exchanger connected between the second brine outlet and the first feed inlet, the method comprising the steps of: changing a pressure between the first brine outlet and the second feed inlet by a first pressure difference ?p.sub.1; changing a pressure between the second brine outlet and the pressure exchanger by a second pressure difference ?p.sub.2 corresponding to the first pressure difference ?p.sub.1; and transferring hydraulic energy from a second brine flow effluent from the second brine outlet to a first feed flow provided to the first feed inlet via the pressure exchanger.
15. The method of claim 14 for operating a system further comprising a third RO stage interconnected between the first RO stage and the second RO stage and having a third feed inlet, a third brine outlet, and a third permeate outlet, the method further comprising the steps of: changing a pressure between the first brine outlet and the third feed inlet by a pressure difference ?p.sub.3,1; changing a pressure between the third brine outlet and the second feed inlet by a pressure difference ?p.sub.3,2; wherein the sum of pressure difference ?p.sub.3,1 and pressure difference ?p.sub.3,2 amounts to at least the first pressure difference ?p.sub.1, and wherein at least one of the pressure difference ?p.sub.3,1 and pressure difference ?p.sub.3,2 is affected via one of a of a hydraulic motor and a hydraulic pump, and the pressure difference ?p.sub.2 is affected by the other one of a hydraulic motor and a hydraulic pump.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The features of the invention become apparent to those skilled in the art by the detailed description of exemplary embodiments with reference to the attached drawings in which:
[0044] FIG. 1 illustrates a system for RO according to a first embodiment;
[0045] FIG. 2 illustrates a system for RO according to a second embodiment;
[0046] FIG. 3 illustrates a system for RO according to a third embodiment;
[0047] FIG. 4 illustrates a system for RO according to a fourth embodiment;
[0048] FIG. 5 illustrates a system for RO according to a fifth embodiment;
[0049] FIG. 6 illustrates a system for RO according to a sixth embodiment;
[0050] FIG. 7 illustrates a system for RO according to a seventh embodiment; and
[0051] FIG. 8 illustrates a method for RO according to an embodiment.
DETAILED DESCRIPTION
[0052] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. Effects and features of the exemplary embodiments, and implementation methods thereof will be described with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and redundant descriptions are omitted. The present invention, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. These embodiments are provided as examples so that this disclosure will be complete and will fully convey the aspects and features of the present invention to those skilled in the art.
[0053] Accordingly, elements not considered necessary to those having skill in the art for a complete understanding of the features of the present invention may not be described.
[0054] As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. Further, the use of may when describing embodiments of the present invention refers to one or more embodiments of the present invention. In the following description of embodiments of the present invention, the terms of a singular form may include plural forms unless the context clearly indicates otherwise.
[0055] It will 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 only used to distinguish one element from another element. For example, a first element may be named a second element and, similarly, a second element may be named a first element, without departing from the scope of the present invention. As used herein, the term substantially, about, and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Further, if the term substantially is used in combination with a feature that could be expressed using a numeric value, the term substantially denotes a range of +/?5% of the value centered on the value.
[0056] FIG. 1 schematically illustrates a system for reverse osmosis, RO, 100 according to a first embodiment, the system 100 comprising a first RO stage 10 and a second RO stage 20.
[0057] The first RO stage 10 comprises a first feed inlet 11, a first brine outlet 12, a first permeate outlet 13 as well as a first high-pressure RO chamber 15 and a first low-pressure RO chamber 16 that are separated by a first RO membrane 14 and, together, form a first RO tank. A first feed flow 17 is fed to the first high-pressure RO chamber 15 via the first RO feed inlet 11 and a first brine flow 19 is discharged via the first brine outlet 12. Further, a first permeate flow 18 is discharged from the first low-pressure RO chamber 16 via a first permeate outlet 13.
[0058] The second RO stage 20 comprises a second feed inlet 21, a second brine outlet 22, a second permeate outlet 23 as well as a second high-pressure RO chamber 25 and a second low-pressure RO chamber 26 that are separated by a second RO membrane 24 and, together, form a second RO tank. A second feed flow 27 is fed to the second high-pressure RO chamber 25 via the second RO feed inlet 21 and a second brine flow 29 is discharged via the second brine outlet 22. Further, a second permeate flow 28 is discharged from the second low-pressure RO chamber 26 via a second permeate outlet 23. Each of the inlets and outlets may be valve controlled, wherein active valves or passive valves (e.g., check valves) may be used. The system further comprises another source of liquid (not shown) to compensate for permeate taken out of system 100 via permeate outlets 13, 23, i.e., to also add to the first feed flow 17.
[0059] The RO system 100 further comprises a pressure exchanger, PE, 40, particularly an isobaric and/or rotary pressure exchanger 40. The pressure exchanger 40 comprises a PE high-pressure inlet 41, a PE HP outlet 42, a HP low-pressure, LP, inlet 43, and a PE LP outlet 44. The PE HP inlet 41 is connected to the second brine outlet 22, i.e., is disposed downstream of the second brine outlet 22, and receives the second brine flow 29 discharged from the second brine outlet 22. The PE HP outlet 42 is connected to the first feed inlet 11, i.e., is disposed upstream of the first feed inlet 11 and provides the first feed flow 17 to the first feed inlet 11. Hence, the PE 40 is connected between the second brine outlet 22 and the first feed inlet 11.
[0060] As illustrated in FIG. 1, a first pressure difference ?p.sub.1 between the first brine outlet 12 and the second feed inlet 21 corresponds to a second pressure difference ?p.sub.2 between the second brine outlet 22 and the pressure exchanger 40. A pressure at the first brine outlet 12 differs from a pressure at the second feed inlet 21 by the first pressure difference ?p.sub.1. Further, a pressure at the second brine outlet 22 differs from a pressure at the PE HP inlet 41 by the second pressure difference ?p.sub.2. Therein, the first pressure difference ?p.sub.1 is preferably greater than 20 bar, more preferably greater than 35 bar, and also preferably even greater than 50 bar. As the second pressure difference ?p.sub.2 corresponds to the first pressure difference ?p.sub.1, also the second pressure difference ?p.sub.2 preferably exceeds those values. The first pressure difference ?p.sub.1 may be exactly the same as the second pressure difference ?p.sub.2 but at least corresponds to about 80% to 120%, preferably to about 90% to 110%, and particularly preferred to about 95% to 105% of the second pressure difference ?p.sub.2.
[0061] Setting the first and second pressure difference ?p.sub.1 and ?p.sub.2 in such corresponding manner provides the advantageous effect that the isobaric pressure exchanger 40 is advantageously operated with optimal energy transfer efficiency. This is achieved as pressure differences, particularly a pressure difference between pressure levels at the PE HP inlet 41 and the PE HP outlet 42 as well as a pressure difference between pressure levels at the PE LP inlet 43 and the PE LP outlet 44 are the same or at least almost the same. By this, optimal pressure conditions and thus transfer efficiency is achieved independent of specific system pressures.
[0062] FIG. 2 schematically illustrates a system for RO 100 according to a second embodiment, wherein same components are denoted with same reference signs as in the first embodiment and a repeated description of these components is omitted for sake of brevity.
[0063] In the system of FIG. 2, the first pressure difference ?p.sub.1 is realized by a (second) hydraulic pump 60.2 and the second pressure difference ?p.sub.2 is realized by a hydraulic motor 50. In other words, the first pressure difference ?p.sub.1 corresponds to the pressure rise at the second hydraulic pump 60.2 and the second pressure difference corresponds to the pressure drop at the hydraulic motor 50. In the system of FIG. 2, the hydraulic motor 50 and the second hydraulic pump 60.2 are connected to each other via a connection that is configured to allow for energy transfer as it is illustrated in FIG. 2 by a dashed line. The energy transfer via that connection may be accomplished hydraulically, mechanically and/or electrically.
[0064] The RO system 100 of FIG. 2 further differs from the system of FIG. 1 in that another (first) hydraulic pump 60.1 is disposed in the first feed flow 17 for pressurizing a part of said feed flow 17. However, a part of said feed flow 17 is split from it upstream the first hydraulic pump 60.1 and provided to the PE LP inlet 43. This part is then pressurized in the isobaric pressure exchanger 40 and provided to the first feed inlet 11 via the PE HP outlet 42. In such manner it can be further advantageously ensured that a volumetric flow into the PE LP inlet 43 matches a volumetric flow into the PE HP inlet 41, which also improves efficiency of PE 40.
[0065] In the embodiment of FIG. 2, the first RO stage 10 operates at a high-pressure level of about 60 bar and the second RO stage 20 operates at a high-pressure level of about 120 bar. In other words, a pressure at the first feed inlet 11 and the first brine outlet 12 is about 60 bar and a pressure at the second feed inlet 21 and the second brine outlet 22 is about 120 bar. A pressure rise at the second hydraulic pump 60.2 is about 60 bar which corresponds to the pressure drop at the hydraulic motor 50 from which energy is transferred to the second hydraulic pump 60.2. A pressure of the second brine flow 29 is about 120 bar upstream and about 60 bar downstream the hydraulic motor 50 and a pressure at the PE HP inlet 41 is about 60 bar, which is about the same as a pressure at first feed inlet 11 and PE HP outlet 42.
[0066] The feed solution may be provided by a feed solution reservoir with a pressure of 2 bar which corresponds to a pressure at the PE LP inlet 43 and to a pressure at a pump inlet of the first hydraulic pump 60.1. A pressure at the PE LP outlet 44 also corresponds to 2 bar and a pressure at a motor outlet of the first hydraulic pump 60.1 is also about 60 bar. Hence, in the system of FIG. 2 pressure levels are ensured for operating the pressure exchanger 40 with an optimal transfer efficiency. Further, the hydraulic energy removed from the system 100 via hydraulic motor 50 for ensuring these pressure levels is reintroduced into the system 100 via second hydraulic pump 60.2 in order to increase the pressure for the second RO stage 20.
[0067] FIG. 3 schematically illustrates a system for RO 100 according to a third embodiment. Therein, same components are denoted with same reference signs as in previous embodiments and a repeated description of these components is omitted for sake of brevity.
[0068] The system 100 of FIG. 3 differs from the system of FIG. 2 in that the first RO stage 10 is operated at a high-pressure level of about 120 bar, while the second RO stage 20 is operated at a high-pressure level of about 60 bar. In other words, a pressure at the first feed inlet 11 and the first brine outlet 12 is about 120 bar and a pressure at the second feed inlet 21 and the second brine outlet 22 is about 60 bar. The system of FIG. 3 further differs from that of FIG. 2 in that hydraulic motor 50 is disposed between the first RO stage 10 and the second RO stage 20, while second hydraulic pump 60.2 is disposed downstream the second brine outlet 22. Hence, in the system 100 of FIG. 3 a pressure drop of about 60 bar is introduced between the first brine outlet 12 and the second feed inlet 21 via the hydraulic motor 50 which corresponds to a pressure rise at the second hydraulic pump 60.2 of about 60 bar. Hence, a pressure of the second brine flow 29 is about 60 bar upstream and about 120 bar downstream the second hydraulic pump 60.2 and thus a pressure at the PE HP inlet 41 is about 120 bar, which is about the same as a pressure at the first feed inlet 11 and the PE HP outlet 42.
[0069] Again, the feed solution may be provided by a feed solution reservoir with a pressure of 2 bar which corresponds to a pressure at the PE LP inlet 43 and to a pressure at a pump inlet of the first hydraulic pump 60.1. A pressure at the PE LP outlet 44 also corresponds to 2 bar and a pressure at a motor outlet of the first hydraulic pump 60.1 is here about 120 bar. Hence, also in the system of FIG. 3 pressure levels are ensured for operating the pressure exchanger 40 with an optimal transfer efficiency and hydraulic energy removed from the system 100 via hydraulic motor 50 is reintroduced into the system 100 via second hydraulic pump 60.2 in order to increase the second brine flow 29 pressure upstream the isobaric pressure exchanger 40.
[0070] FIG. 4 schematically illustrates a system for RO 100 according to a fourth embodiment. Therein, same components are denoted with same reference signs as in previous embodiments and a repeated description of these components is omitted for sake of brevity.
[0071] The system 100 of FIG. 4 differs from that of FIG. 3 in that the connection between the hydraulic motor 50 and the second hydraulic pump 60.2 is realized via an induction motor 70. The induction motor 70 may be an asynchronous motor that has a stator and a rotor. The second hydraulic pump 60.2 may be an axial piston pump and the hydraulic motor 50 may be an axial piston motor. The rotor of the induction motor 70 may be mechanically connected to an input shaft of the axial piston pump 60.2 and to an output shaft of the axial piston motor 50. The rotor of the induction motor 70 may be connected to a motor shaft of the induction motor 70 that is connected to the input shaft and the output shaft and wherein this motor shaft may be either a single continuous motor shaft or may be formed by pair of dual (double) motor shafts.
[0072] The use of the configuration as of FIG. 4 advantageously allows for transferring energy from the hydraulic motor 50 to the second hydraulic pump 60.2 in a particularly efficient manner, i.e., without conversion losses for a conversion from mechanical to electrical energy as it might appear e.g., in a variable frequency drive or the like. Further, the use of induction motor 70 for mechanically connecting the hydraulic motor 50 and the second hydraulic pump 60.2 further advantageously provides ways for efficient control of the system 100, e.g., by adding additional energy being required by second hydraulic pump 60.2 for creating a desired pressure level at the PE HP inlet 41. This may be varied by changing a slip of induction motor 70. Further, at least one of the hydraulic motor 50 and the second hydraulic pump 60.2 comprises a swash plate and/or a mechanical gear to enable an adjustment of a volume and/or revolution ratio between the hydraulic motor 50 and the second hydraulic pump 60.2.
[0073] FIG. 5 schematically illustrates a system for RO 100 according to a fifth embodiment. Therein, same components are denoted with same reference signs as in previous embodiments and a repeated description of these components is omitted for sake of brevity. The system 100 of FIG. 5 has a same configuration of hydraulic motor 50 and second hydraulic pump 60.2 as described with reference to FIG. 2 that are connected to each other via induction motor 70, which provides the advantages as described with respect to FIG. 4.
[0074] FIG. 6 schematically illustrates a system for RO 100 according to a sixth embodiment. Therein, same components are denoted with same reference signs as in previous embodiments and a repeated description of these components is omitted for sake of brevity.
[0075] The RO system 100 of FIG. 6 further comprises a third RO stage 30 comprising a third feed inlet 31, a third brine outlet 32, a third permeate outlet 33 as well as a third high-pressure RO chamber 35 and a third low-pressure RO chamber 36 that are separated by a third RO membrane 34 and, together, form a third RO tank. A third feed flow 37 is fed to the third high-pressure RO chamber 35 via the third RO feed inlet 31 and a third brine flow 39 is discharged via the third brine outlet 32. Further, a third permeate flow 38 is discharged from the third low-pressure RO chamber 36 via a third permeate outlet 33. The permeate of all three RO stages 10, 20, 30 may be provided commonly or separately to subsequent stages or uses.
[0076] In the system 100 of FIG. 6, a first pressure difference ?p.sub.1 between the first RO stage 10 and the second RO stage 20 is constituted by a pressure difference ?p.sub.3,1 between the first RO stage 10 and the third RO stage 30 and by a pressure difference ?p.sub.3,2 between the third RO stage 30 and the second RO stage 20. As discussed with respect to the embodiments of FIGS. 7 and 8 at least one of the pressure differences ?p.sub.3,1 and ?p.sub.3,2 is created by one of a hydraulic motor and a hydraulic pump. The system 100 could further comprise additional RO stages between the third RO stage 30 and the second RO stage 20, e.g., 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 ?p.sub.3,2 would be further divided into pressure differences ?p.sub.4,1 and ?p.sub.4,2 and the pressure difference ?p.sub.4,2 would be further divided into pressure differences ?p.sub.5,1 and ?p.sub.5,2, at least some of which are created by one of a hydraulic motor and a hydraulic pump. Again, system 100 comprises another source of liquid (not shown) to compensate for permeate taken out of system 100 via permeate outlets 13, 23, 33, i.e., to also add to the first feed flow 17.
[0077] FIG. 7 schematically illustrates a system for RO 100 according to a seventh embodiment. Therein, same components are denoted with same reference signs as in previous embodiments and a repeated description of these components is omitted for sake of brevity.
[0078] The embodiment of FIG. 7 corresponds to that of FIG. 6, wherein each of the pressure differences ?p.sub.3,1 and ?p.sub.3,2 is created by a hydraulic pump, namely 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, a pressure at the first feed inlet 11 and the first brine outlet 12 is about 60 bar, a pressure at the third feed inlet 31 and the third brine outlet 32 is about 90 bar, and a pressure at the second feed inlet 21 and the second brine outlet 22 is about 120 bar. A pressure rise at the first hydraulic pump 60.1 is thus about 30 bar and a pressure rise at the second hydraulic pump 60.2 is also about 30 bar. The sum of these pressure rises, i.e., 60 bar, corresponds to the pressure drop at the hydraulic motor 50 from which energy is transferred to both of the first hydraulic pump 60.1 and the second hydraulic pump 60.2 as indicated by the dashed lines. A pressure of the second brine flow 29 is about 120 bar upstream and about 60 bar downstream the hydraulic motor 50 and thus a pressure at the PE HP inlet 41 is about 60 bar, which is about the same as a pressure at the first feed inlet 11 and at the PE HP outlet 42. Again, system 100 comprises another source of liquid (not shown) to compensate for permeate taken out of system 100 via permeate outlets 13, 23, 33, i.e., to also add to the first feed flow 17.
[0079] FIG. 8 schematically illustrates a block diagram of a method for operating a system for reverse osmosis, RO, 100 as previously described with respect to FIGS. 1 to 8 according to an embodiment. Therein, the method comprises the step S100 of changing a pressure between the first brine outlet 12 and the second feed inlet 21, preferably via one of a hydraulic motor 50 and a hydraulic pump 60, by a first pressure difference ?p.sub.1. The method further comprises the step S200 of changing a pressure between the second brine outlet 22 and the pressure exchanger 40, preferably via another one of the hydraulic motor 50 and a hydraulic pump 60, by a second pressure difference ?p.sub.2 corresponding to the first pressure difference ?p.sub.1. The method further comprises the step S300 of transferring hydraulic energy from a second brine flow 28 effluent from the second brine outlet 22 to a first feed flow 17 provided to the first feed inlet 11 via the pressure exchanger 40. This method allows for an operation of a multi-stage RO system 100 with at least two RO stages 10, 20 with improved energy efficiency by utilizing hydraulic energy created via a pressure drop at the hydraulic motor 50 to generate a pressure rise at the hydraulic pump 60 and by feeding the pressure exchanger 40 with a flow, the pressure of which is optimized by said pressure drop or said pressure rise for improved transfer efficiency.
