WO2016141321A1 - Vacuum-assisted forward osmosis system - Google Patents

Vacuum-assisted forward osmosis system Download PDF

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Publication number
WO2016141321A1
WO2016141321A1 PCT/US2016/020961 US2016020961W WO2016141321A1 WO 2016141321 A1 WO2016141321 A1 WO 2016141321A1 US 2016020961 W US2016020961 W US 2016020961W WO 2016141321 A1 WO2016141321 A1 WO 2016141321A1
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WO
WIPO (PCT)
Prior art keywords
vacuum
forward osmosis
osmosis system
chamber
recited
Prior art date
Application number
PCT/US2016/020961
Other languages
French (fr)
Inventor
Reza Aini
Adel Obaid SHARIF
Original Assignee
Qatar Foundation For Education, Science And Community Development
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Filing date
Publication date
Application filed by Qatar Foundation For Education, Science And Community Development filed Critical Qatar Foundation For Education, Science And Community Development
Publication of WO2016141321A1 publication Critical patent/WO2016141321A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/445—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by forward osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/002—Forward osmosis or direct osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/002—Forward osmosis or direct osmosis
    • B01D61/0022—Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/002—Forward osmosis or direct osmosis
    • B01D61/0023—Accessories; Auxiliary operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/14—Pressure control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/12—Specific discharge elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/30—Specific dilution or de-ionizing chambers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/60—Specific sensors or sensor arrangements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/90—Additional auxiliary systems integrated with the module or apparatus
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/40—Liquid flow rate
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/06—Pressure conditions
    • C02F2301/063—Underpressure, vacuum
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Definitions

  • the present invention relates to forward osmosis, and particularly to a vacuum- assisted forward osmosis system.
  • water from a lower osmotic pressure solution is transferred to a higher osmotic pressure solution through a semi-permeable membrane.
  • the semi-permeable membrane is disposed between the two solutions and physically separates the two solutions from each other.
  • the transport of water is limited by the osmotic pressure difference; i.e., the higher the difference, the higher the water or solvent flux will be.
  • the draw solution becomes diluted. Dilution of the draw solution reduces the osmotic pressure difference. The reduced osmotic pressure difference reduces the driving force for water transport across the membrane.
  • the vacuum-assisted forward osmosis system includes a housing having a source water chamber, a draw solution chamber, and a vacuum chamber in communication with the draw solution chamber.
  • the source water chamber can include source water, e.g., seawater or brackish water.
  • the draw solution chamber can include draw solution, e.g., brine.
  • the source water chamber and the draw solution chamber are divided by a selective membrane, i.e., a semi-permeable membrane.
  • the draw solution chamber includes one or more perforated columns. Each column is positioned in the path of water flowing through the membrane from the source water chamber in order to extract the water and thereby minimize dilution of the draw solution. Each column directs the extracted water to the vacuum chamber below the draw solution chamber.
  • the vacuum-assisted forward osmosis system can thereby avoid or minimize a reduction in the osmotic pressure difference between the two chambers.
  • Fig. 1 is a plan view in section of a vacuum-assisted forward osmosis system according to the present invention.
  • Fig. 2 is a side view in section of a vacuum-assisted forward osmosis system according to the present invention.
  • Fig. 3A is a front view of a vacuum-assisted forward osmosis system according to the present invention.
  • Fig. 3B is a side view of a vacuum-assisted forward osmosis system according to the present invention.
  • Fig. 4 is a side view in section of the vacuum chamber in a vacuum-assisted forward osmosis system according to the present invention.
  • Fig. 5 is a top view in section of an alternative embodiment of a column in a vacuum- assisted forward osmosis system according to the present invention.
  • Fig. 6 is front view of the column shown in Fig. 5.
  • Fig. 7 is a top view in section of an alternative embodiment of a column in a vacuum- assisted forward osmosis system according to the present invention.
  • Fig. 8 is front view of the column shown in Fig. 7.
  • the vacuum-assisted forward osmosis system 10 includes a housing 12 having a source water chamber 14, a draw solution chamber 16, and a vacuum chamber 52 that is in communication with the draw solution chamber 16.
  • the source water chamber 14 can include source water 18, e.g., seawater or brackish water.
  • the draw solution chamber 16 can include draw solution 20, e.g., brine.
  • the source water chamber 14 and the draw solution chamber 16 are divided by a selective membrane 22, e.g., a semi-permeable membrane.
  • the membrane 22 can be, for example, a flat membrane screen for forward osmosis.
  • the draw solution chamber 16 can have a higher osmotic pressure than the source water chamber 14.
  • Both the source water chamber 14 and the draw solution chamber 16 include at least one inlet pipe and at least one air venting port.
  • the source water chamber 14 includes a first inlet pipe 24, a second inlet pipe 26, and an air venting port 32.
  • the draw solution chamber 16 also includes a first inlet pipe 28, a second inlet pipe 30, and an air venting port 34.
  • the air venting ports 32, 34 ensure a water-tight and bubble-free supply of solution in each chamber 14, 16.
  • the draw solution chamber 16 includes one or more perforated columns 36a, 36b including a central duct 48.
  • the central duct 48 is in fluid communication with the vacuum-chamber 52 (Fig. 2) disposed at the bottom of the draw solution chamber 16.
  • Each column 36a, 36b is positioned in the path of water exiting the membrane from the source water chamber 14 to extract the newly diluted draw solution in the draw solution chamber 16, thereby minimizing dilution of the remaining draw solution and avoiding or minimizing a reduction in the osmotic pressure difference between the two chambers 14, 16.
  • the columns 36a, 36b direct the diluted draw solution to the vacuum chamber 52 through the central duct 48.
  • each column 36a, 36b has an arcuate rear wall 38 and a substantially
  • the arcuate wall 38 can be curved or generally C-shaped, and includes opposing curved or winged ends 42a and 42b that extend toward the membrane 22 but are spaced from the membrane 22.
  • the front wall 40 can include a first longitudinal wall 40a and an extension 40b that extends normal to the first wall 40a.
  • the first wall 40a extends between and connects the opposing ends 42a and 42b of the arcuate wall 38.
  • the extension 40b can contact the membrane 22 along the height of the membrane 22.
  • a first series of orifices 44a and a second series of orifices 44b, respectively, can be defined in the first wall 40a between the first wall 40a and opposing ends 42a and 42b respectively, of the arcuate wall 38.
  • a third series of orifices 46a and a fourth series of orifices 46b, respectively, can be defined in the first wall 40a between the first wall 40a and opposing sides of the extension 40b.
  • the first, second, third, and fourth series of orifices, 44a, 44b, 46a, and 46b, can be elliptical and extend vertically with respect to the height of the columns 36a, 36b.
  • the central opening or duct 48 is in fluid communication with the first, second, third, and fourth series of orifices 44a, 44b, 46a, and 46b.
  • the central duct 48 is connected with an exit port 50.
  • the exit port 50 is in fluid communication with the vacuum-chamber 52 (Fig. 2) disposed at a bottom of the draw solution chamber 16.
  • Fig. 3A shows a front view of an exemplary column 36a.
  • the first and second series of orifices 44a and 44b can be aligned along opposing ends 42a and 42b respectively of the arcuate wall 38.
  • the third and fourth series of orifices 46a and 46b can be aligned along opposing sides of the extension 40b.
  • each column 36a, 36b can include one or more seals.
  • each column can include a top flat seal 54 on a top wall of the column, a bottom flat seal 56 on a bottom wall of the column, one or more annular seals 58 on the exit port 50 of the column, and a curved face seal 60 on the curved arcuate wall 38 of the column.
  • the vacuum chamber 52 includes a vacuum pump 62.
  • the vacuum pump 62 can be in communication with the exit port 50.
  • the vacuum chamber 52 can include level sensors 64a, 64b extending from opposing side walls of the vacuum chamber 52 and a pair of shut off valves 66a, 66b connected to a top wall of the vacuum chamber 52.
  • a relief valve 68 can be disposed in a bottom wall of the vacuum chamber 52.
  • the vacuum chamber 52 can be depressurized and hermetically sealed.
  • the vacuum pump 62 is configured to provide a suction force, pulling diluted draw solution into the central opening 48 through the first, second, third, and fourth series of orifices.
  • the suction force initiated by the vacuum pump 62 creates a vacuum zone between the columns 36a, 36b and the semi-permeable membrane 22.
  • the vacuum zone can pull the draw solution 20 that is situated behind each column 36a, 36b towards the semi-permeable membrane 22 to serve as bait or provide increased osmotic pressure difference between the draw solution 20 and the source water 18 closest to the membrane 22 surface, thereby facilitating extraction of water from the source water chamber 14.
  • the suction force in each column 36a, 36b can simultaneously draw diluted draw solution 20 into the columns 36a, 36b while pulling draw solution 20 from behind the columns 36a, 36b towards the semi-permeable membrane 22.
  • a desalination cycle begins by depressurizing the vacuum chamber 52 to an appropriate level, i.e., a level at which the sensors 64a, 64b are horizontally disposed. In this position, the shut off valves 66a, 66b below the columns 36a, 36b, are in the “off position and the pressure relief valve 68 at the base of the vacuum chamber 52 is also in the "off position.
  • the static pressure of the diluted draw solution 20 inside the vacuum chamber is always greater than atmospheric pressure outside (by design).
  • the pressure relief valve 68 opens and discharges the collected diluted draw solution 20, forcing the level sensors 64a, 64b to drop down from the horizontal position and opening the shut off valves 66a, 66b beneath the columns 36a, 36b. Consequently, all of the newly diluted draw solution 20 in the draw solution chamber 16 between the membrane 22 and the columns 36a, 36b is sucked into the collection duct 48, and subsequently into the depressurized vacuum chamber 52.
  • the difference in pressure that is created in the vacuum chamber 52 creates a low pressure zone between the columns 36a, 36b and the surface of the membrane 22 in the draw solution chamber 16.
  • the pressure difference forces the solution behind the columns to flow toward the membrane.
  • the draw solution 20 flows toward the membrane 22 through a space between the columns 36a, 36b or along the curved sides 42 of the columns (Fig. 1).
  • the combination of the curved ends 42 of the columns 36a, 36b in conjunction with the membrane 22 surface creates a converging-diverging wedge that functions similar to a throttling valve to regulate the volume of the draw solution entering the "vacuum zone" (shown in Fig. 2).
  • a second collection duct 70 can be provided, which extends through the extension 40b (Fig. 5). As shown in Figs. 5 and 6, and the first and second series of orifices 44a, 44b can extend horizontally between each end of the arcuate wall 38 and the extension 40b. The first and second series of orifices 44a and 44b can be centered between the extension 40b and a respective end 42a and 42b of the arcuate wall 38. The third and fourth series of orifices 46a, 46b can be defined in opposing sides of the extension 40b, in communication with the second collection duct 70.
  • each column can include only one collection duct 48, and first and second series of orifices 44a, 44b that extend horizontally between each end 42a and 42b of the arcuate wall 38 and the extension 40b.
  • the first and second series of orifices 44a and 44b can extend in a staggered fashion along the length of the column.

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  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The vacuum-assisted forward osmosis system (10) includes a housing (12) having a source water chamber (14), a draw solution chamber (16), and a vacuum chamber (52) in communication with the draw solution chamber (16). The draw solution chamber (16) has a higher osmotic pressure than the source water chamber (14). The source water chamber (14) and the draw solution chamber (16) are divided by a selective membrane (22). The draw solution chamber (16) has one or more perforated columns (36a, 36b). Each column (36a, 36b) is positioned in the path of water flowing through the membrane (22) from the source water chamber (14) in order to extract draw solution (20) that has mixed with the water and thereby minimize dilution of the draw solution (20). Each column (36a, 36b) directs the extracted water to the vacuum chamber (52) below the draw solution chamber (16).

Description

VACUUM-ASSISTED FORWARD OSMOSIS SYSTEM
TECHNICAL FIELD
The present invention relates to forward osmosis, and particularly to a vacuum- assisted forward osmosis system. BACKGROUND ART
In forward osmosis, water from a lower osmotic pressure solution is transferred to a higher osmotic pressure solution through a semi-permeable membrane. The semi-permeable membrane is disposed between the two solutions and physically separates the two solutions from each other. The transport of water is limited by the osmotic pressure difference; i.e., the higher the difference, the higher the water or solvent flux will be.
Most conventional forward osmosis membranes are made of two layers, a dense separation layer and a support layer. The dense layer, where the separation of the solutes occurs, is normally much thinner than the support layer. Water is frequently trapped in the support layer. The trapped water reduces the osmotic pressure difference, and hence reduces the water flux. This phenomenon, called "Internal Concentration Polarization" (ICP), can have a negative impact on the performance of the forward osmosis membrane.
Further, when transferred water gets mixed with the draw solution, the draw solution becomes diluted. Dilution of the draw solution reduces the osmotic pressure difference. The reduced osmotic pressure difference reduces the driving force for water transport across the membrane.
Thus, a vacuum-assisted forward osmosis system addressing the aforementioned problems is desired.
DISCLOSURE OF INVENTION
The vacuum-assisted forward osmosis system includes a housing having a source water chamber, a draw solution chamber, and a vacuum chamber in communication with the draw solution chamber. The source water chamber can include source water, e.g., seawater or brackish water. The draw solution chamber can include draw solution, e.g., brine. The source water chamber and the draw solution chamber are divided by a selective membrane, i.e., a semi-permeable membrane. The draw solution chamber includes one or more perforated columns. Each column is positioned in the path of water flowing through the membrane from the source water chamber in order to extract the water and thereby minimize dilution of the draw solution. Each column directs the extracted water to the vacuum chamber below the draw solution chamber. The vacuum-assisted forward osmosis system can thereby avoid or minimize a reduction in the osmotic pressure difference between the two chambers.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view in section of a vacuum-assisted forward osmosis system according to the present invention.
Fig. 2 is a side view in section of a vacuum-assisted forward osmosis system according to the present invention.
Fig. 3A is a front view of a vacuum-assisted forward osmosis system according to the present invention.
Fig. 3B is a side view of a vacuum-assisted forward osmosis system according to the present invention.
Fig. 4 is a side view in section of the vacuum chamber in a vacuum-assisted forward osmosis system according to the present invention.
Fig. 5 is a top view in section of an alternative embodiment of a column in a vacuum- assisted forward osmosis system according to the present invention.
Fig. 6 is front view of the column shown in Fig. 5.
Fig. 7 is a top view in section of an alternative embodiment of a column in a vacuum- assisted forward osmosis system according to the present invention.
Fig. 8 is front view of the column shown in Fig. 7.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
BEST MODES FOR CARRYING OUT THE INVENTION
Referring to Figs. 1 and 2, the vacuum-assisted forward osmosis system 10 includes a housing 12 having a source water chamber 14, a draw solution chamber 16, and a vacuum chamber 52 that is in communication with the draw solution chamber 16. The source water chamber 14 can include source water 18, e.g., seawater or brackish water. The draw solution chamber 16 can include draw solution 20, e.g., brine. The source water chamber 14 and the draw solution chamber 16 are divided by a selective membrane 22, e.g., a semi-permeable membrane. The membrane 22 can be, for example, a flat membrane screen for forward osmosis. The draw solution chamber 16 can have a higher osmotic pressure than the source water chamber 14. Fresh water flows naturally from the source water chamber 14 through the membrane 22 to the draw solution chamber 16. Both the source water chamber 14 and the draw solution chamber 16 include at least one inlet pipe and at least one air venting port. For example, the source water chamber 14 includes a first inlet pipe 24, a second inlet pipe 26, and an air venting port 32. The draw solution chamber 16 also includes a first inlet pipe 28, a second inlet pipe 30, and an air venting port 34. The air venting ports 32, 34 ensure a water-tight and bubble-free supply of solution in each chamber 14, 16. The draw solution chamber 16 includes one or more perforated columns 36a, 36b including a central duct 48. The central duct 48 is in fluid communication with the vacuum-chamber 52 (Fig. 2) disposed at the bottom of the draw solution chamber 16.
Because of the osmotic pressure difference between the two chambers, water flows naturally through the membrane from the source water chamber to the draw solution chamber in accordance with the principles of forward osmosis. Columns 36a and 36b can minimize mixing of the water flowing into the draw solution chamber 16 through the membrane 22 with the draw solution in the draw solution chamber 16. Each column 36a, 36b is positioned in the path of water exiting the membrane from the source water chamber 14 to extract the newly diluted draw solution in the draw solution chamber 16, thereby minimizing dilution of the remaining draw solution and avoiding or minimizing a reduction in the osmotic pressure difference between the two chambers 14, 16. The columns 36a, 36b direct the diluted draw solution to the vacuum chamber 52 through the central duct 48.
In further detail, each column 36a, 36b has an arcuate rear wall 38 and a substantially
T-shaped front wall 40. The arcuate wall 38 can be curved or generally C-shaped, and includes opposing curved or winged ends 42a and 42b that extend toward the membrane 22 but are spaced from the membrane 22. The front wall 40 can include a first longitudinal wall 40a and an extension 40b that extends normal to the first wall 40a. The first wall 40a extends between and connects the opposing ends 42a and 42b of the arcuate wall 38. The extension 40b can contact the membrane 22 along the height of the membrane 22. A first series of orifices 44a and a second series of orifices 44b, respectively, can be defined in the first wall 40a between the first wall 40a and opposing ends 42a and 42b respectively, of the arcuate wall 38. A third series of orifices 46a and a fourth series of orifices 46b, respectively, can be defined in the first wall 40a between the first wall 40a and opposing sides of the extension 40b. The first, second, third, and fourth series of orifices, 44a, 44b, 46a, and 46b, can be elliptical and extend vertically with respect to the height of the columns 36a, 36b. The central opening or duct 48 is in fluid communication with the first, second, third, and fourth series of orifices 44a, 44b, 46a, and 46b. The central duct 48 is connected with an exit port 50. The exit port 50 is in fluid communication with the vacuum-chamber 52 (Fig. 2) disposed at a bottom of the draw solution chamber 16.
Fig. 3A shows a front view of an exemplary column 36a. As shown, the first and second series of orifices 44a and 44b can be aligned along opposing ends 42a and 42b respectively of the arcuate wall 38. The third and fourth series of orifices 46a and 46b can be aligned along opposing sides of the extension 40b. Referring to Figs. 3 A and 3B, each column 36a, 36b can include one or more seals. For example, each column can include a top flat seal 54 on a top wall of the column, a bottom flat seal 56 on a bottom wall of the column, one or more annular seals 58 on the exit port 50 of the column, and a curved face seal 60 on the curved arcuate wall 38 of the column.
As shown more clearly in Fig. 4, the vacuum chamber 52 includes a vacuum pump 62. The vacuum pump 62 can be in communication with the exit port 50. The vacuum chamber 52 can include level sensors 64a, 64b extending from opposing side walls of the vacuum chamber 52 and a pair of shut off valves 66a, 66b connected to a top wall of the vacuum chamber 52. A relief valve 68 can be disposed in a bottom wall of the vacuum chamber 52. The vacuum chamber 52 can be depressurized and hermetically sealed.
The vacuum pump 62 is configured to provide a suction force, pulling diluted draw solution into the central opening 48 through the first, second, third, and fourth series of orifices. The suction force initiated by the vacuum pump 62 creates a vacuum zone between the columns 36a, 36b and the semi-permeable membrane 22. The vacuum zone can pull the draw solution 20 that is situated behind each column 36a, 36b towards the semi-permeable membrane 22 to serve as bait or provide increased osmotic pressure difference between the draw solution 20 and the source water 18 closest to the membrane 22 surface, thereby facilitating extraction of water from the source water chamber 14. In other words, the suction force in each column 36a, 36b can simultaneously draw diluted draw solution 20 into the columns 36a, 36b while pulling draw solution 20 from behind the columns 36a, 36b towards the semi-permeable membrane 22.
In further detail, a desalination cycle according to the present teachings begins by depressurizing the vacuum chamber 52 to an appropriate level, i.e., a level at which the sensors 64a, 64b are horizontally disposed. In this position, the shut off valves 66a, 66b below the columns 36a, 36b, are in the "off position and the pressure relief valve 68 at the base of the vacuum chamber 52 is also in the "off position. The static pressure of the diluted draw solution 20 inside the vacuum chamber is always greater than atmospheric pressure outside (by design). Hence, as soon as the pressure head of the draw solution 20 reaches a certain limit, the pressure relief valve 68 opens and discharges the collected diluted draw solution 20, forcing the level sensors 64a, 64b to drop down from the horizontal position and opening the shut off valves 66a, 66b beneath the columns 36a, 36b. Consequently, all of the newly diluted draw solution 20 in the draw solution chamber 16 between the membrane 22 and the columns 36a, 36b is sucked into the collection duct 48, and subsequently into the depressurized vacuum chamber 52. Since the solution in both the source water chamber 14 and the draw solution chamber 16 is bubble-free (i.e., no air trapped in the system), there is a continuous supply of diluted draw solution that is fed into the depressurized vacuum chamber 52 and discharged at the same rate, making the flow uni-directional.
The difference in pressure that is created in the vacuum chamber 52 creates a low pressure zone between the columns 36a, 36b and the surface of the membrane 22 in the draw solution chamber 16. The pressure difference forces the solution behind the columns to flow toward the membrane. The draw solution 20 flows toward the membrane 22 through a space between the columns 36a, 36b or along the curved sides 42 of the columns (Fig. 1). The combination of the curved ends 42 of the columns 36a, 36b in conjunction with the membrane 22 surface creates a converging-diverging wedge that functions similar to a throttling valve to regulate the volume of the draw solution entering the "vacuum zone" (shown in Fig. 2). Once the draw solution 20 enters the throat of the converging-diverging wedge, a natural forward osmosis process takes place, and the resulting diluted draw solution 20 is collected and diverted toward the core collecting duct 48 of the columns 36a, 36b through the elliptical orifices.
It should be understood that the configuration of the columns 36a, 36b can be different from that described above. For example, in addition to the collection duct 48, a second collection duct 70 can provided, which extends through the extension 40b (Fig. 5). As shown in Figs. 5 and 6, and the first and second series of orifices 44a, 44b can extend horizontally between each end of the arcuate wall 38 and the extension 40b. The first and second series of orifices 44a and 44b can be centered between the extension 40b and a respective end 42a and 42b of the arcuate wall 38. The third and fourth series of orifices 46a, 46b can be defined in opposing sides of the extension 40b, in communication with the second collection duct 70. Alternatively, as shown in Figs. 7 and 8, each column can include only one collection duct 48, and first and second series of orifices 44a, 44b that extend horizontally between each end 42a and 42b of the arcuate wall 38 and the extension 40b. As shown more clearly in Fig. 8, the first and second series of orifices 44a and 44b can extend in a staggered fashion along the length of the column.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Claims

CLAIMS We claim:
1. A vacuum-assisted forward osmosis system, comprising:
a housing having a source water chamber including source water and a draw solution chamber;
a selective membrane separating the source water chamber and the draw solution chamber;
at least one perforated column in the draw solution chamber, the at least one perforated column having a perforated side wall defining a plurality of openings, the at least one perforated column defining a central duct in communication with the plurality of openings; and
a vacuum chamber including a vacuum pump, the vacuum chamber being in fluid communication with the central duct.
2. The vacuum-assisted forward osmosis system as recited in claim 1, wherein the at least one perforated column includes an arcuate rear wall and a substantially T-shaped front wall.
3. The vacuum-assisted forward osmosis system as recited in claim 2, wherein the arcuate rear wall includes a pair of opposed curved ends, the pair of opposed curved ends extending toward the selective membrane.
4. The vacuum-assisted forward osmosis system as recited in claim 3, wherein the substantially T-shaped front wall includes a first longitudinal wall and an extension portion extending normal to the first longitudinal wall.
5. The vacuum-assisted forward osmosis system as recited in claim 4, wherein the first longitudinal wall extends between and connects the pair of opposed curved ends of the arcuate wall.
6. The vacuum-assisted forward osmosis system as recited in claim 5, wherein the extension portion of the substantially T-shaped front wall contacts the selective membrane.
7. The vacuum-assisted forward osmosis system as recited in claim 6, wherein the plurality of openings comprise a first series of orifices and a second series of orifices, respectively, formed through the first longitudinal wall and the pair of opposed curved ends of the arcuate wall.
8. The vacuum-assisted forward osmosis system as recited in claim 7, wherein the plurality of openings further comprise a third series of orifices and a fourth series of orifices, respectively, formed through the first longitudinal wall and opposing sides of the extension portion.
9. The vacuum-assisted forward osmosis system as recited in claim 8, wherein each said opening of the first, second, third and fourth series of orifices are substantially elliptical.
10. The vacuum-assisted forward osmosis system as recited in claim 9, wherein each of the first, second, third and fourth series of orifices extends vertically with respect to a height of the at least one perforated column.
11. The vacuum-assisted forward osmosis system as recited in claim 1, wherein the vacuum chamber comprises at least one level sensor.
12. The vacuum-assisted forward osmosis system as recited in claim 11, wherein the vacuum chamber further comprises at least one shut off valve.
13. The vacuum-assisted forward osmosis system as recited in claim 12, wherein the vacuum chamber further comprises at least one relief valve.
14. A vacuum- assisted forward osmosis system, comprising:
a housing having a source water chamber including source water and a draw solution chamber;
a selective membrane separating the source water chamber and the draw solution chamber;
at least one perforated column in the draw solution chamber, the at least one perforated column having a perforated side wall defining a plurality of openings, the at least one perforated column defining a central duct in communication with the plurality of openings; and
a vacuum chamber including a vacuum pump, at least one shut off valve and at least one relief valve, the vacuum chamber being in fluid communication with the central duct.
15. The vacuum-assisted forward osmosis system as recited in claim 14, wherein the at least one perforated column includes an arcuate rear wall and a substantially T-shaped front wall.
16. The vacuum-assisted forward osmosis system as recited in claim 15, wherein the arcuate rear wall includes a pair of opposed curved ends, the pair of opposed curved ends extending toward the selective membrane.
17. The vacuum-assisted forward osmosis system as recited in claim 16, wherein the substantially T-shaped front wall includes a first longitudinal wall and an extension portion extending normal to the first longitudinal wall.
18. The vacuum-assisted forward osmosis system as recited in claim 17, wherein the first longitudinal wall extends between and connects the pair of opposed curved ends of the arcuate wall.
19. The vacuum-assisted forward osmosis system as recited in claim 18, wherein the plurality of openings comprise a first series of orifices and a second series of orifices, respectively, formed through the first longitudinal wall and the pair of opposed curved ends of the arcuate wall.
20. The vacuum-assisted forward osmosis system as recited in claim 19, wherein the plurality of openings further comprise a third series of orifices and a fourth series of orifices, respectively, formed through the first longitudinal wall and opposing sides of the extension portion.
PCT/US2016/020961 2015-03-04 2016-03-04 Vacuum-assisted forward osmosis system WO2016141321A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5938939A (en) * 1995-12-29 1999-08-17 Rhone-Poulenc Agrochimie Suction device enabling fine solid particles to be separated from a liquid
US6306307B1 (en) * 2000-03-07 2001-10-23 Fielding Chemical Technologies, Inc. Pervaporation apparatus and method
US20030034303A1 (en) * 2001-08-07 2003-02-20 Olson Jeffrey A. Method of filtering a fluid and apparatus therefor
US20110084008A1 (en) * 2009-10-13 2011-04-14 Stanislaw Kielbowicz Increased efficiency strainer system
US20130112603A1 (en) * 2010-04-28 2013-05-09 Stx Heavy Industries Co., Ltd. Forward osmotic desalination device using membrane distillation method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5938939A (en) * 1995-12-29 1999-08-17 Rhone-Poulenc Agrochimie Suction device enabling fine solid particles to be separated from a liquid
US6306307B1 (en) * 2000-03-07 2001-10-23 Fielding Chemical Technologies, Inc. Pervaporation apparatus and method
US20030034303A1 (en) * 2001-08-07 2003-02-20 Olson Jeffrey A. Method of filtering a fluid and apparatus therefor
US20110084008A1 (en) * 2009-10-13 2011-04-14 Stanislaw Kielbowicz Increased efficiency strainer system
US20130112603A1 (en) * 2010-04-28 2013-05-09 Stx Heavy Industries Co., Ltd. Forward osmotic desalination device using membrane distillation method

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