WO2009072894A1

WO2009072894A1 - Apparatus and method for exchanging pressure between fluid flows

Info

Publication number: WO2009072894A1
Application number: PCT/NO2008/000427
Authority: WO
Inventors: Arvid Ophaug
Original assignee: Eureka Gruppen As
Priority date: 2007-12-03
Filing date: 2008-12-02
Publication date: 2009-06-11
Also published as: EP2240412A1; NO20076210L

Abstract

An apparatus for exchanging pressure between fluids , comprising at least one housing arranged with at least one, preferably two, fluid inlets and with at least one, preferably two, fluid outlets and an inner space. The inner space accommodates a pressure exchanger unit arranged with at least one pressure transferring element dividing the inner space of the pressure exchanger unit into at least a first and a second chamber. Each chamber is provided with at least one flow passage, the pressure exchanger unit being movably arranged in the housing to position at least one flow passage in line with at least one of the fluid inlets or fluid outlets for the transport of fluid into and out of each chamber. The invention also comprise a method for exchanging pressure between fluids.

Description

Apparatus and method for exchanging pressure between fluid flows

The invention concerns an apparatus and a method for exchanging pressure between fluid flows. Various apparatuses and methods for exchanging pressure between fluid flows are known in the art.

The object of the invention is to provide an apparatus and a method, which improve the prior art solutions.

The object of the invention is obtained by an apparatus and a method as defined in the independent claims. Further embodiments of the invention is defined in the following dependent claims.

In accordance with the independent claim 1 , an apparatus for exchanging pressure between fluids is defined. The apparatus comprises at least one housing arranged with at least one, preferably two, fluid inlets and with at least one, preferably two, fluid outlets. As the skilled person will understand, the number of fluid inlets and fluid outlets may vary depending on application wherein the apparatus is used. Each housing is provided with an inner space accommodating a pressure exchanger unit arranged with at least one pressure transferring element dividing the inner space of the pressure exchanger unit into at least a first and a second chamber. Each chamber is provided with at least one flow passage. The pressure exchanger unit is movably arranged in the housing to position at least one flow passage in line with at least one of the fluid inlets or fluid outlets for the transport of fluid into and out of each chamber. The number of flow passages arranged in the pressure exchanger unit may vary according to the field of use of the apparatus. Further, the number of flow passages and the positioning and configuration of the flow passages, may be adapted depending on those of the fluid inlets and fluid outlets. In one embodiment the number of fluid inlets and fluid outlets are four, and the number of flow passages are two. In one aspect of the invention the fluid inlets and the fluid outlets may be spaced at essentially opposite positions at the perimeter of the housing. Consequently, the flow passages may then be spaced at essentially opposite positions at the perimeter of the pressure exhanger unit.

In accordance with the independent method claim, a method for exchanging pressure between fluids by the use of at least one apparatus alternating between a first and a second operating mode is defined. In a further method two pressure exchanger units are used, wherein one pressure exchanger unit is in a first operating mode, while the other pressure exchanger unit is in a second operating mode and vice versa, for the continuous delivery of pressurized fluid.

The pressure transferring element arranged in the apparatus has technical features for transferring the pressure of fluid accommodated in one of the chambers to the fluid accommodating the other chamber of the pressure exchanger unit. Further, the pressure transferring element is provided so that no mixing of the fluids of the two chambers occurs. The pressure transferring element may be implented in various ways. For instance it may be provided as a movable piston or it may be arranged as a membrane in between the two chambers. The membrane has characteristics enabling an increase of volume in one chamber when fluid is let into the chamber and a reduction of volume in the other chamber. These characteristics may for instance be provided by the kind of material used (in some or all parts of the membrane), the particular design of the membrane or a combination of design and material For instance the membrane may be made in silicon.

In one embodiment the membrane alternates between two configurations depending on which chamber the fluid is entering. In one position of the of the pressure exchanger one of the chambers is filled with fluid, the membrane is then displayed in first configuration. When repositioning the pressure exchanger, fluid is let into the other chamber. The filling of this chamber, causes at least a portion of the membrane to shift into the second configuration as a result of the increase of volume in the one of the chambers. In the second configuration the membrane may be transformed into the inverted version or mirror version of the first configuration, for instance the membrane is turned inside out assuming the same shape as in the first configuration, but facing the opposite direction. In the two configurations the membranes may have essentially the same shape, but displayed as inverted versions. Portions of the membrane may be fixed in the pressure exchanger, while at least one portion of the membrane is provided to be shifted from one position to another position. In one version, the size of the area of the membrane may be greater than the size of the cross section of the membrane. By this provision of the membrane, the filling of one of the chambers causes the inversion of the membrane or turning the membrane inside out.

The membrane may have a shape wherein the load applied on the membrane will be present as bending stress in the membrane, thereby preventing damage due to fatigue occurring in the membrane as a result of repetitious load impact.

If an excessive filling of the chamber should result in an overfilled chamber, the membrane will experience stretching. The material of the membrane endures an expansion of 1000% before collapse.

In one embodiment the apparatus in accordance with the invention comprises two housings. The first housing is arranged with a first pressure exchanger unit and the second housing is arranged with a second pressure exchanger unit. By this arrangement the apparatus is the prepared for bringing the pressure exchanger units into alternate working conditions, ensuring that one of the pressure exchanger units delivers a fluid flow at a pressure level sufficient to process wherein the apparatus is to be included. In this embodiment, when filling fluid into a first chamber of the first pressure exchanger unit, fluid is transported out of a second chamber of the first pressure exchanger unit. When filling fluid into a second chamber of the second pressure exchanger unit, fluid is transported out of a first chamber of the second pressure exchanger unit. In an apparatus according to this embodiment, the apparatus is capable of delivering a continuous fluid flow at a certain pressure level, by using two pressure exchanger units working alternately.

Further, in a filling position of the first chamber, a flow passage of the first chamber may be aligned with a first fluid inlet for the flow of fluid into the first chamber. A flow passage of the second chamber may then be aligned with a second fluid outlet for the transport of fluid out of the second chamber. Preferably, the fluid entering the first chamber pressurizes the fluid in the second chamber. In a filling position of the second chamber, a flow passage of the second chamber may be aligned with a second fluid inlet for the flow of fluid into the second chamber. A flow passage of the first chamber may be aligned with a first fluid outlet for the transport of fluid out of the chamber. Preferably, the fluid entering the first chamber pressurizes the fluid in the second chamber.

To bring the apparatus into the different operating modes, wherein the various flow passages are aligned with fluid inlets and fluid outlets for letting fluid into or out of the chambers, the apparatus is provided with a drive unit to move the pressure exchanger unit between the various positions. The pressure exchanger unit may be rotatably arranged in the housing, thereby providing the movement of the pressure exchanger unit as a rotation movement. As the skilled person will understand, the movements may be other than rotation, preferably by arrangements providing a reliable and simple solution for moving the pressure exchanger unit between the positions in the housing.

The pressure exchanger unit may be comprised by a cylinder unit fitting into the inner space of the housing, wherein in the inner space may be cylindrical adapted to the shape of the cylinder unit. In this arrangement the cylinder unit may be supported by suitable means in the housing, so that the cylinder unit may rotate about its longitudinal axis. The suitable means may be constituted by projections arranged at the end portions of the cylinder unit and extending in the longitudinal direction of the pressure exchanger unit. Providing support for the movement such as rotation of pressure exchanger unit may be achieved by various means. Also the provision of the housing and cylinder unit may be carried out in various ways. The housing and cylinder unit may be in one part or constituted by several parts, and the cylinder unit may rotate in one piece, or the various part may rotate separately.

The pressure exchanger unit may be manufactured in a corrosion resistant material.

The apparatus and the method may be used in various applications such as desalination of water, cleaning of water and other processes wherein the fluid experiences loss of pressure. If the invention is to be included in a desalination process, the fluid entering the first chamber of the first pressure exchanger unit may comprise seawater, for instance low pressure seawater. Further, the fluid leaving the second chamber of the first pressure exchanger unit may comprise brine, for instance low pressure brine. The fluid entering the second chamber of the second pressure exchanger unit may comprise brine for instance high pressure brine and the fluid leaving the first chamber of the second pressure exchanger unit may comprise seawater, for instance high pressure seawater. An example of use of the invention in a desalination plant will be described in more detail with reference to the figures. An example of the invention will be described in the following with reference to the figs wherein

Fig 1 shows a perspective view of the energy recover apparatus.

Fig 2 shows an exploded view of an energy recover apparatus in accordance with the invention as shown in fig 1.

Fig 3a-d show the flow of fluid through the energy recover apparatus shown in fig

1.

Fig 4 shows the energy recover apparatus included in a process for desalinating water by reverse osmosis.

Fig 1 and 2 shows an example of an apparatus 1 for exchanging pressure. In the figures 1 and 2 the apparatus 1 comprises a first and a second housing 2 and 3. Each housing 2, 3 is shown constituted by two housing parts 2a, 2b and 3a, 3b respectively, connected to each other by suitable fixing means thereby making up a cylindrical shaped structure. As the skilled person will realize, the housings may be constructed otherwise and may assume various shapes within the scope of the invention. Also, the apparatus may be constituted by one housing including all necessary parts as described below, or more than two housings may make up the apparatus. The two housings 2, 3 are each provided with two main inlets 4, 5 and two main outlets 6, 7. Each main inlet 4, 5 branches into two fluid inlets 4a, 4b and 5a, 5b. Each main outlet 6, 7 branches into two fluid outlets 6a, 6b and 7a, 7b.

A first pressure exchanger unit 8 is accommodated in the first housing 2 and a second pressure exchanger unit 9 is accommodated in the second housing 3. The first and second pressure exchanger units 8, 9 are each provided by two cup shaped element fitted together forming a cylindrical unit fitting into the inner space of the housing 2, 3. A membrane 10, 11 is arranged in between the cup shaped elements, separating each pressure exchanger unit 8, 9 into first and second chambers 8a, 8b and 9a, 9b respectively. The membranes 10 and 11 are provided to allow for an increase of volume in of one of the adjacent chambers 9a, 9b and 8a, 8b, and the subsequent reduction of volume in the other chamber. Further, the membranes have characteristics preventing the mix of fluids contained in the chambers separated by the membrane.

Flow passages 14, 15, 16 are arranged making a through opening in the wall of each cup shaped element, thereby providing for the communication with each of the chambers 8a, 8b, 9a, 9b. Chamber 9b is also provided with a flow passage, but as the flow passages are shown at different positions around the perimeter, the flow passage of chamber 9b is not visible in fig 2. The first and second pressure exchanger units 8, 9 are supported in the housing by shafts 18, 19 projecting from the cup shaped elements. As shown in the figs 1 and 2, one end of the shafts of the first and second pressure exchanger units 8, 9 protrude through the housing parts 2a, 3b for the engagement of drive wheels 20, 21. The drive wheels 20, 21 are connected to a drive unit such as for instance an electric motor, hydraulic motor or other means for supplying driving power. By the arrangement of the drive wheels 20, 21 connected to the shafts 18, 19, the first and second pressure exchanger units 8, 9 are arranged to be rotated in the belonging housing 2, 3 moving the flow passages between positions wherein the flow through the individual fluid passage is closed, or the fluid passage is positioned corresponding with the fluid outlet or fluid inlet for the communication of flow into or out of the chamber.

The flow passages have a width corresponding to the diameter of the fluid outlets and fluid inlets to provide for adequate communication of fluid into and out of the chambers. As shown in fig 1 and 2, the flow passages have an oblong shape with a longitudinal extension in the perimeter direction. By this shape of the flow passage it is possible to provide a solution wherein a flow is communicated into or out of the individual chamber also during the rotation of the first and second pressure exchanger units 8, 9, as the longitudinal extension of the flow passage corresponds to an angular rotation of the first pressure exchanger unit 8, 9. In fig 2, the flow passages 14, 15 are given different locations at the perimeter of the first pressure exchanger unit 8. The angular displacement of the flow passages 14, 15 correspond to the fitting with the fluid inlet and fluid outlets for the flow into and out of each of the chambers 8a and 8b, as will be described in detail with reference to fig 3a-3d. The adjustment of the configuration of the flow passages around the perimeter of one of the pressure exchanger units, based on the positions of the flow passages of the other pressure exchanger unit, provides an arrangement for the continuous work of the apparatus. This will be described further with reference to fig 3a-3d. Fig 3a and fig 3b are sectional views of the first pressure exchanger unit 8 in the housing 3 as shown in figs 1 and 2. Fig 3c and fig 3d are sectional views of the second pressure exchanger unit 9 in the housing 2 as shown in figs 1 and 2.

In the figs 3a-3d sleeve elements 40a, 40b, 40c, 4Od are shown arranged between the housings 2, 3 and first and second pressure exchanger units 8, 9 respectively. The sleeve elements facilitates the rotation of the pressure exchanger units 8, 9, and have also a sealing function to avoid leakage in between the housings 2, 3 and the pressure exchanger units 8, 9, when fluid flow through the flow passages 14, 15, 16, 17.

In figs 3a and 3c a first operating mode of the first and second pressure exchanger units 8, 9 is shown. This concerns an emptying procedure for the second chamber 8b, 9b, caused by the filling of the first chamber 8a, 9a. This emptying procedure prepares the second chamber 8b, 9b for the filling of pressurizing fluid to pressurize fluid filled into first chamber 8a, 9a. This is shown in figs 3b, 3d, showing the first and second pressure exchanger units 8, 9 in a second operating mode. To ensure a continuous deliverance of pressurized fluid the operation modes of the first and second pressure exchanger units 8, 9 are arranged alternately, wherein one of the first and second pressure exchanger units 8, 9 assumes a first operating mode while the other is in a second operating mode and vice versa.

In the figs 3a-3d the membranes 10, 11 are shown in an embodiment wherein the design of the membrane provides for the increase of volume in one of the chambers. The membrane is provided with the size of the cross section smaller than the size of the area of one face of the membrane. In the version shown the perimeter of the membrane is fixed in the pressure exchanger 8, 9, and the membrane further comprises a middle portion 10a, 11a and a surrounding curved portion 10a, 10b. By this shape at least one portion of the membrane 10, 11 is easily shifted from one position as shown in fig 3a, 3d to another position as shown in fig 3b, 3d.

In fig 3 a the first pressure exchanger unit 8 has been rotated so that the flow passage 14 of the first chamber 8a is positioned in line with the fluid inlet 4b. The flow passage 15 of the second chamber 8a is positioned in line with the fluid outlet 7b. In this position the fluid inlet 5b and the fluid outlet 6b are closed. Fluid flows into the first chamber 8a through the fluid inlet 4b and the flow passage 14 as shown by arrow Sl, and displaces the fluid of chamber 8b which leaves the chamber 8b through the flow passage 15 and fluid outlet 7b as shown by arrow Bl . The pressure of the fluid entering the first chamber 8a is transferred to the fluid of the second chamber 8b by the membrane 10. The membrane has flexible properties and portions of the membrane shifts into the second chamber 8b, due to increase of volume in the first chamber 8a, thereby reducing the volume of fluid in the second chamber 8b and pressurizing the fluid contained herein. The pressure of the fluid in the second chamber 8b thereby equals the pressure level of the fluid in the first chamber 8 a.

In fig 3b the fluid passage 14 of the first chamber 8a is rotated into a position aligning the fluid passage 14 with the fluid outlet 6b. The fluid passage 15 of the second chamber 8b is aligned in position with the fluid inlet 5b, for the filling of the second chamber 8b through the fluid inlet 5 b and the flow passage 15 as shown by arrow B2. By the filling of fluid into the second chamber 8b, the portions of the membrane 10 shifts into the first chamber 8a and pressurizes the fluid at a pressure level of the fluid of the first chamber 8a, which essentially equals the pressure level of the fluid entering the second chamber 8b. Fluid leaves the first chamber 8a through the flow passage 14 and the fluid outlet 6b as shown by arrow S2. The configuration of flow passages, fluid inlets and outlets, as well as the fluid transfer into and out of the chambers as shown for the second pressure exchanger unit 9 in fig 3b correspond to the condition of the first pressure exchanger unit 8 as shown in fig 3a. Likewise the condition of the second pressure exchanger unit 9 as shown in fig 3d corresponds to that in fig 3a. The first and second pressure exchanger units 8, 9 may be prepared for a continuous rotation or the rotation may be executed abruptively. During the continuous rotation, the individual rotation of the first and second pressure exchanger units 8, 9 is adjusted so that the alternation of the operating condition of each first and second pressure exchanger units 8, 9 as shown in fig 3a-3d is continuously achieved. When the first and second pressure exchanger units 8, 9 are arranged for abruptive rotation, the individual pressure exchanger unit may rotate only a portion of a full rotation at a time positioning the first and second pressure exchanger units 8, 9 in operating modes as shown in fig 3a-3d.

In one embodiment of the invention an apparatus including two pressure exchanger units are to be included into a process in need of a continuous feed of fluid of a certain pressure level. In such an application the pressure exchanger units are employed so that the pressure exchanger units work alternately. When the first pressure exchanger unit 8 is employed in first operating mode as shown in fig 3 a, the second pressure exchanger unit 9 is employed in second operating mode as shown in fig 3c. And when the first pressure exchanger unit 8 is employed in first operating mode as shown in fig 3b, the second pressure exchanger unit 9 is employed in second operating mode as shown in fig 3d. By this an arrangement is provided wherein one or the other pressure exchanger unit constantly delivers a fluid having the necessary working pressure to one of the devices in the process loop.

In one embodiment the apparatus is included in a process for desalinating of water by reverse osmosis using a membrane module. The apparatus of the invention is installed in this arrangement to make use of brine, otherwise discharged at sea, leaving the membrane module at relatively high pressure. Fig 4 shows an example of a desalinating system of this kind. Low pressure salt water, for instance at about 1-2 bar is let into the system at inlet point 20. The low pressure salt water is fed to a high pressure pump 21 pressurizing the low pressure salt water to a membrane pressure level and thereafter feeding the membrane pressure to a membrane module 30 for desalination. Desalted water is discharged from the membrane module at discharging point 23 due to the reverse osmosis process occurring in the membrane module, whereas a rest portion of the salt water experiences a further concentration when passing through the membrane module 22 and leaves the membrane module at discharging point 23 as high pressure brine B2 entering the apparatus 1 to be used as means for pressurizing fluid as shown in fig 1, 2, 3a-d. When using the apparatus 1 in a system as the one shown in fig 4, the flow Sl entering the first chamber 8a, 9a as shown in the emptying procedure of figs 3a and 3d, is constituted by low pressure salt water as supplied through intake 21 in fig 4. The flow Bl out of the second chamber 8b, 9b corresponds to the low pressure brine Bl let out at the dumping point 24 in fig 4 for instance at a pressure level of 1-2 bar. In the second operating mode of the first and second pressure exchanger units 8, 9, see fig 3b and 3c, the flow B2 entering the second chamber 8b, 9b correspond to the high pressure brine B2 leaving the discharging point 23 of the membrane module 22 in fig 4. The flow of brine B2 is used for pressurizing the fluid in the first chamber 8a, 9a, before the fluid leaves the chamber shown as flow S2. In this embodiment the flow S2 corresponds to the salt water supplied from the apparatus for exchanging pressure 1 to a booster pump 31 in fig 4 for the further pressurizing before entering the membrane module 22 as shown in the fig 4. The pressure of brine B2 may be at about 63 bar and then consequently the salt water S2 is pressurized to about 63 bar in the pressure exchanger units 8, 9.

Claims

1. An apparatus (1) for the exchanging pressure between fluids, characterized in that the apparatus comprises

-at least one housing (2, 3) arranged with at least one, preferably two, fluid inlets (4, 5) and with at least one, preferably two, fluid outlets (6, 7) and an inner space accommodating a pressure exchanger unit (8, 9) arranged with at least one pressure transferring element dividing the inner space of the pressure exchanger unit (8, 9) into at least a first and a second chamber (8a, 8b, 9a, 9b), wherein each chamber is provided with at least one flow passage, the pressure exchanger unit (8, 9) being movably arranged in the housing

(2, 3) to position at least one flow passage in line with at least one of the fluid inlets (4, 5) or fluid outlets (6, 7) for the transport of fluid into and out of each chamber.

2. An apparatus in accordance with claim 1, characterized in thatit comprises a first and second pressure exchanger unit (8, 9) each arranged in a housing for the alternating -filling of fluid into a first chamber (8a) of the first pressure exchanger unit (8) and the transport of fluid out of a second chamber (8b) of the first pressure exchanger unit, - filling of fluid into a second chamber (9b) of the second pressure exchanger unit (9) and the transport of fluid out of a first chamber (9a) of the second pressure exchanger unit.

3. An apparatus in accordance with one of the proceeding claims, characterized in that -in a filling position of the first chamber (8a, 9a), a flow passage of the first chamber (8a, 9a) is aligned with a fluid inlet for the flow of fluid into the chamber, and a flow passage of the second chamber (8b, 9b) is aligned with a fluid outlet for the transport of fluid out of the second chamber, -in a filling position of the second chamber (8b, 9b), a flow passage of the second chamber is aligned with a fluid inlet for the flow of fluid into the second chamber (8b, 9b), and a flow passage of the first chamber (8a, 9a) is aligned with a first fluid outlet for the transport of fluid out of the first chamber (8a, 9a).

4. An apparatus in accordance with one of the proceeding claims, characterized in that a drive unit is provided to move the pressure exchanger unit (8, 9).

5. An apparatus in accordance with one of the proceeding claims, characterized in that the pressure exchanger unit (8, 9) is rotatably arranged in the housing (2, 3).

6. An apparatus in accordance with one of the proceeding claims, characterized in that the pressure exchanger unit (8, 9) is comprised by a cylinder unit fitting into the inner space of the housing (2, 3).

7. An apparatus in accordance with claim 6, characterized in that the cylinder unit is supported by suitable means in the housing (2, 3), for the rotation of the cylinder unit about its longitudinal axis.

8. An apparatus in accordance with one of the proceeding claims, characterized in that the configuration of the flow passages depends on the configuration of the fluid inlets and fluid outlets.

9. An apparatus in accordance with one of the proceeding claims, characterized in that the pressure transferring element comprises a movable piston or a membrane (10, 11).

10. An apparatus in accordance with one of the proceeding claims, characterized in that the fluid entering the first chamber (8a) of the first pressure exchanger unit (8) comprises seawater, for instance low pressure seawater.

11. An apparatus in accordance with one of the proceeding claims, characterized in that the fluid leaving the second chamber (8b) of the first pressure exchanger unit (8) comprises brine, for instance low pressure brine.

12. An apparatus in accordance with one of the proceeding claims, characterized in that the fluid entering the second chamber (9b) of the second pressure exchanger unit (9) comprises brine, for instance high pressure brine.

13. An apparatus in accordance with one of the proceeding claims, characterized in that the fluid leaving the first chamber (9a) of the second pressure exchanger unit (9) comprises seawater, for instance high pressure seawater,

14. Method for exchanging pressure between fluids by the use of at least one pressure exchanger unit (8, 9) arranged in a housing (2, 3), alternating between two operating modes, characterized in that in

-a first operating mode the pressure exchanger unit (8, 9) which is movably arranged in the housing (2, 3), moves to a position wherein a flow passage of a first chamber (8a, 9a) of the pressure exchanger unit (8, 9) aligns with an fluid inlet (4,5) arranged in the housing (2, 3), and a flow passage of a second chamber (8b, 9b) of the pressure exchanger unit (8, 9) aligns with an fluid outlet (6, 7) arranged in the housing (2, 3), wherein a flow of fluid fills the first chamber (8a, 9a) and pressurizes the fluid of the second chamber (8b, 9b) by means of a pressure transferring element separating the two chambers, and the flow of fluid thereafter leaves the second chamber (8b, 9b), and in -a second operating mode the pressure exchanger unit (8, 9) moves to a position wherein a flow passage of a second chamber (8b, 9b) of the pressure exchanger unit (8, 9) aligns with an fluid inlet (4, 5) arranged in the housing, and a flow passage of a first chamber (8a, 9a) of the pressure exchanger unit (8, 9) aligns with an fluid outlet (6, 7) arranged in the housing (2, 3), wherein a flow of fluid fills the second chamber (8b, 9b) and pressurizes the fluid of the first chamber (8a, 9a) by means of the pressure transferring element, and the flow of fluid thereafter leaves the first chamber (8a, 9a).

15. Method in accordance with claim 14, by the use of two pressure exchanger units (8, 9) each arranged in a housing (2, 3), wherein one pressure exchanger unit (8) is in a first operating mode, while the other pressure exchanger unit (9) is in a second operating mode and vice versa, for the continuous delivery of pressurized fluid.