WO2019097261A1 - Solvent separation - Google Patents
Solvent separation Download PDFInfo
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- WO2019097261A1 WO2019097261A1 PCT/GB2018/053347 GB2018053347W WO2019097261A1 WO 2019097261 A1 WO2019097261 A1 WO 2019097261A1 GB 2018053347 W GB2018053347 W GB 2018053347W WO 2019097261 A1 WO2019097261 A1 WO 2019097261A1
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- WIPO (PCT)
- Prior art keywords
- solution
- semi
- permeable membrane
- initial
- feed
- Prior art date
Links
- 239000002904 solvent Substances 0.000 title claims abstract description 31
- 238000000926 separation method Methods 0.000 title description 3
- 239000012528 membrane Substances 0.000 claims abstract description 233
- 239000000243 solution Substances 0.000 claims abstract description 193
- 239000012527 feed solution Substances 0.000 claims abstract description 73
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 61
- 238000000034 method Methods 0.000 claims abstract description 60
- 239000012466 permeate Substances 0.000 claims abstract description 47
- 238000009292 forward osmosis Methods 0.000 claims description 15
- 230000003204 osmotic effect Effects 0.000 claims description 15
- 239000002243 precursor Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 26
- 150000003839 salts Chemical class 0.000 description 15
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 11
- 239000002357 osmotic agent Substances 0.000 description 8
- 239000002440 industrial waste Substances 0.000 description 6
- 239000013535 sea water Substances 0.000 description 6
- 239000011780 sodium chloride Substances 0.000 description 6
- 239000002351 wastewater Substances 0.000 description 6
- 239000000835 fiber Substances 0.000 description 5
- 239000012267 brine Substances 0.000 description 4
- 150000001805 chlorine compounds Chemical class 0.000 description 4
- -1 for example Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 239000012266 salt solution Substances 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 239000002154 agricultural waste Substances 0.000 description 3
- 239000003673 groundwater Substances 0.000 description 3
- 238000001728 nano-filtration Methods 0.000 description 3
- 239000002352 surface water Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- 229920002284 Cellulose triacetate Polymers 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 239000004952 Polyamide Substances 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical class OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 2
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000004645 aluminates Chemical class 0.000 description 2
- 230000003373 anti-fouling effect Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 150000001642 boronic acid derivatives Chemical class 0.000 description 2
- SXDBWCPKPHAZSM-UHFFFAOYSA-M bromate Chemical class [O-]Br(=O)=O SXDBWCPKPHAZSM-UHFFFAOYSA-M 0.000 description 2
- 150000001649 bromium compounds Chemical class 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical class OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 229920002301 cellulose acetate Polymers 0.000 description 2
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical class [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 150000001913 cyanates Chemical class 0.000 description 2
- 238000010612 desalination reaction Methods 0.000 description 2
- 150000004673 fluoride salts Chemical class 0.000 description 2
- UQSQSQZYBQSBJZ-UHFFFAOYSA-M fluorosulfate group Chemical group S(=O)(=O)([O-])F UQSQSQZYBQSBJZ-UHFFFAOYSA-M 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 150000004694 iodide salts Chemical class 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 150000002825 nitriles Chemical class 0.000 description 2
- 150000002826 nitrites Chemical class 0.000 description 2
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical class OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 2
- 235000021317 phosphate Nutrition 0.000 description 2
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 2
- 229920002647 polyamide Polymers 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000002455 scale inhibitor Substances 0.000 description 2
- 150000004760 silicates Chemical class 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Chemical class 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 238000004630 atomic force microscopy Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
Classifications
-
- 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
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
-
- 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
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
- B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
-
- 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
- B01D2311/25—Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed
- B01D2311/252—Recirculation of concentrate
- B01D2311/2521—Recirculation of concentrate to permeate side
-
- 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
- B01D2311/25—Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed
- B01D2311/253—Bypassing of feed
- B01D2311/2531—Bypassing of feed to permeate side
-
- 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
Definitions
- the present invention relates to a process for separating a solvent, for example, water from a feed solution.
- water is separated from an impure solution, for example, a saline solution.
- Various methods of water purification are known.
- An example of such a method is reverse osmosis.
- reverse osmosis water is forced from a region of high solute concentration through a semipermeable membrane to a region of low solute concentration by applying a hydraulic pressure in excess of the osmotic pressure of the high solute concentration solution.
- Reverse osmosis is commonly used, for example, to obtain drinking water from seawater.
- Reverse osmosis is also used to separate water from, for example, industrial waste streams. By using reverse osmosis to treat industrial waste streams, it is possible to generate relatively clean water from industrial waste, while reducing the volume of undesirable waste requiring disposal or further treatment.
- Reverse osmosis requires relatively high pressures to be exerted on the high solute concentration side of the membrane.
- pressures as high as 82 barg are commonly used to increase the recovery of product water. This places a significant energy burden on desalination methods that rely on conventional reverse osmosis.
- streams having higher solute concentrations than seawater may require even higher hydraulic pressures to be applied.
- Many commercially available reverse osmosis membranes are unsuitable for withstanding hydraulic pressures of greater than 82 barg.
- Figure 1 is a schematic illustration of a system for carrying out a process according to a first example of the present disclosure
- Figure 2 is a schematic illustration of a system for carrying out a process according to a second example of the present disclosure
- Figure 3 is a schematic illustration of a system for carrying out a process according to a third example of the present disclosure
- Figure 4 is a schematic illustration of a system for carrying out a process according to a fourth example of the present disclosure
- Figure 5 is a schematic illustration of a system for carrying out a process according to a fifth example of the present disclosure.
- Figure 6 is a schematic illustration of a system for carrying out a process according to a sixth example of the present disclosure.
- Figure 7 is a schematic illustration of a system for carrying out a process according to a seventh example of the present disclosure.
- Figure 8 is a schematic illustration of a system for carrying out a process according to an eighth example of the present disclosure.
- Figure 9 is a schematic illustration of a system for carrying out a process according to a ninth example of the present disclosure.
- Figure 10 is a schematic illustration of a system for carrying out a process according to a tenth example of the present disclosure.
- Figure 11 is a schematic illustration of a system for carrying out a process according to an eleventh example of the present disclosure
- a process for separating solvent from a feed solution comprising:
- the solvent is water.
- the feed solution may be a salt solution, for example, a saline solution.
- the feed solution may be an impure water stream, for example, saline ground water or surface water, brine and seawater.
- Other examples include waste water streams, lake water, river water and pond water. Examples of waste water streams include industrial or agricultural waste water streams.
- the feed solution may be a salt solution that is prepared by dissolving an osmotic agent in water.
- the present inventors have found that, by feeding a portion of the feed solution or a portion of the residual solution to the permeate-side of the first semi-permeable membrane, the osmotic pressure difference across the first semi-permeable membrane may be reduced. As a result, the hydraulic pressure required to induce solvent flow from the feed solution by reverse osmosis may be reduced.
- the reverse osmosis step therefore, can become osmotically assisted (i.e. osmotically assisted reverse osmosis or “OARO”). Accordingly, the flux across the semi-permeable membrane is higher compared to that achievable using reverse osmosis alone operating under the same hydraulic pressure limitations.
- An important advantage of the present invention is that it allows highly concentrated feed solutions to be treated at hydraulic pressures that are within the hydraulic pressure ratings of conventional reverse osmosis membranes (e.g.82 barg or less). With conventional reverse osmosis techniques, such highly concentrated feed solutions would require hydraulic pressures in excess of the maximum hydraulic pressure rating of most conventional reverse osmosis membranes (e.g. above 82 barg).
- it is a portion of the feed solution that is fed to the permeate- side of the first semi-permeable membrane.
- Making use of a portion of the residual solution to feed to the permeate-side of the first semi-permeable membrane may be advantageous because of the concentrated nature of the residual solution.
- a lower flow of residual solution to the permeate-side of the first semi-permeable membrane may be required in comparison to a flow of feed solution, for example, in order to provide the same brine concentration. This may result from the higher osmotic pressure of the residual solution.
- a more concentrated residual solution may be obtained for a given hydraulic pressure.
- feeding a portion of the residual solution may be more energy efficient than feeding, for example, a portion of the feed solution.
- the lower pressure drop down the fibre bore may mean than less energy is required.
- the feed solution to the first semi-permeable membrane may be produced by contacting an initial solution with one side of an initial semi-permeable membrane. Hydraulic pressure may be applied to the initial solution, such that solvent from the initial solution can flow through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi- permeable membrane and an initial residual solution on the feed-side of the initial semi- permeable membrane.
- the initial residual solution may be employed as the feed solution to the first semi-permeable membrane.
- the initial permeate solution may be withdrawn, for example, for use or further purification.
- Withdrawing the initial permeate solution for use after the initial reverse osmosis stage may advantageously produce a higher quality permeate, in comparison to feeding the initial permeate solution to further reverse osmosis steps. This may result from the lower concentration in the feed/concentrate side of the initial semi-permeable membrane. Additionally, the inclusion of an initial reverse osmosis step may provide economic benefits, as conventional, widely used reverse osmosis may be employed. In one embodiment, a portion of the permeate solution on the permeate side of the first semi-permeable membrane may be recycled as a feed to the initial semi- permeable membrane.
- the hydraulic pressure applied to the initial solution may be used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane.
- a pump may be used to apply hydraulic pressure to drive the initial solution through the initial semi-permeable membrane.
- This hydraulic pressure may also be used fully or in part to drive downstream membrane separation steps.
- the process further comprises withdrawing at least a portion of the residual solution on the feed-side of the first semi-permeable membrane and contacting the withdrawn solution with one side of a further semi-permeable membrane as a further feed solution.
- Hydraulic pressure may be applied to the further feed solution in contact with the further semi-permeable membrane to cause solvent from the further feed solution to flow through the further semi-permeable membrane by reverse osmosis to provide a further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane.
- a portion of the further feed solution or a portion of the further residual solution may be fed to the permeate-side of the further semi-permeable membrane. As explained above, this can reduce the osmotic pressure difference across the further semi- permeable membrane. The hydraulic pressure required to induce solvent flow from the further feed solution by reverse osmosis may hence be reduced.
- hydraulic pressure may be applied using a dedicated pump, it is possible to use a pump employed to apply hydraulic pressure to the initial solution in an initial reverse osmosis step to apply hydraulic pressure for one or more of any subsequent osmotically assisted reverse osmosis steps.
- a series of further semi-permeable membranes may be provided downstream of the first semi-permeable membrane.
- the residual solution from any one of these membranes may be withdrawn and contacted with a downstream membrane as a feed solution for the downstream membrane.
- a portion of the feed solution to the downstream membrane or a portion of the residual solution on the feed-side of the downstream membrane may be fed to the permeate-side of the downstream membrane.
- a portion of the further permeate solution on the permeate side of the further semi-permeable membrane may be recycled as or as part of a feed to the initial semi-permeable membrane.
- the feed solution to the first semi-permeable membrane is produced by contacting an initial solution with one side of an initial semi-permeable membrane. Hydraulic pressure may be applied to the initial solution, such that solvent from the initial solution flows through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi- permeable membrane and an initial residual solution on the feed-side of the initial semi- permeable membrane. The initial residual solution may then be contacted with one side of a further semi-permeable membrane.
- Hydraulic pressure may be applied to the initial residual solution, such that solvent from the initial residual solution flows through the further semi-permeable membrane by reverse osmosis to provide a further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane.
- the further residual solution may then be used as the feed to the first semi-permeable membrane.
- the initial residual solution may flow through a series of further semi-permeable membranes, each producing its respective permeate and residual solutions. At least one of these residual solutions may be used as the feed to the first semi-permeable membrane.
- At least a portion of the further residual solution from the (or one of the) further semi-permeable membrane is withdrawn and fed to the permeate- side of the first semi-permeable membrane.
- At least a portion of the first permeate solution from the first semi-permeable membrane is recycled as a feed to the initial semi-permeable membrane.
- the hydraulic pressure applied to the initial solution is used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane and/or the further feed solution that is contacted with the or at least one of the further semi-permeable membranes.
- the feed solution and/or the initial solution may be any solution, such as an aqueous solution.
- the feed solution and/or the initial solution may be a salt solution, for example, an aqueous salt solution.
- the feed solution and/or the initial solution may contain a plurality of dissolved salts.
- the feed solution and/or the initial solution is an aqueous solution of sodium chloride.
- suitable feed solutions and/or the initial solutions include saline ground water or surface water, brine and seawater. Other examples include waste water streams, lake water, river water and pond water. Examples of waste water streams include industrial or agricultural waste water streams.
- the feed solution and/or the initial solution may be a solution of one or more osmotic agents.
- Suitable osmotic agents include salts, such as inorganic salts.
- Suitable salts include salts of ammonium and metals, such as alkali metals (e.g. Li, Na, K) and alkali earth metals (e.g. Mg and Ca).
- the salts may be fluorides, chlorides, bromides, iodides, sulphates, sulphites, sulphides, carbonates, hydrogencarbonates, nitrates, nitrites, nitrides, phosphates, aluminates, borates, bromates, carbides, chlorides, perchlorates, hypochlorates, chromates, fluorosilicates, fluorosulphates, silicates, cyanides and cyanates.
- One or more salts may be present.
- An example may be sodium chloride.
- the total dissolved salt concentration of the feed solution and/or the initial solution may be at least 5,000 mg/I, for example, 5,000 to 250,000 mg/I. In one example, the total dissolved salt concentration of the feed solution and/or the initial solution to the first semi- permeable membrane is at least 30,000 mg/I.
- the osmotic pressure of the feed may be at least 4 barg, for example, 4 to 320 barg.
- the initial solution may be produced by contacting an impure solution with one side of a forward osmosis membrane, and contacting the opposite side of the forward osmosis membrane with an initial solution precursor.
- the osmotic pressure (solute concentration) of the initial solution precursor may be higher than the osmotic pressure (solute concentration) of the impure solution such that solvent from the impure solution flows across the forward osmosis membrane by forward osmosis to dilute the initial solution precursor to produce the initial solution.
- the impure solution may be saline ground water or surface water, brine and seawater.
- Other examples include waste water streams, lake water, river water and pond water.
- Examples of waste water streams include industrial or agricultural waste water streams.
- the initial solution and/or initial solution precursor may be formed by dissolving an osmotic agent in a solvent, for example, water.
- Suitable osmotic agents include salts, such as sodium chloride.
- salts include salts of ammonium and metals, such as alkali metals (e.g. Li, Na, K) and alkali earth metals (e.g. Mg and Ca).
- the salts may be fluorides, chlorides, bromides, iodides, sulphates, sulphites, sulphides, carbonates, hydrogencarbonates, nitrates, nitrites, nitrides, phosphates, aluminates, borates, bromates, carbides, chlorides, perchlorates, hypochlorates, chromates, fluorosilicates, fluorosulphates, silicates, cyanides and cyanates.
- One or more salts may be employed.
- the semi-permeable membrane(s) employed in the present invention may be nanofiltration or reverse osmosis membranes.
- the semi-permeable membrane is a reverse osmosis membrane. Where more than two membranes are employed, the membranes may be the same or different.
- the semi-permeable membrane(s) are all reverse osmosis membranes.
- the semi- permeable membrane(s) are all nanofiltration membranes.
- both nanofiltration and reverse osmosis membranes are employed as the semi-permeable membrane(s).
- any suitable reverse osmosis membrane may be used in the present invention.
- the reverse osmosis membrane may have an average (e.g. mean) pore size of 0.5 to 80 Angstroms, preferably, 2 to 50 Angstroms.
- the membrane has an average (e.g. mean) pore size of from 3 to 30 Angstroms.
- Pore size e.g. mean pore size
- a differential flow method may be employed (Japan Membrane Journal, vol. 29; no. 4; pp. 227 -235 (2004)) or the use of salts, uncharged solutes and atomic force microscopy (Journal of Membrane Science 126 (1997) 91-105).
- Suitable reverse osmosis membranes include integral membranes and composite membranes.
- suitable membranes include membranes formed of cellulose acetate (CA) and/or cellulose triacetate (CTA) , such as or similar to those used in the study of McCutcheon et al . Desalination 174 (2005) 1-11 and membranes formed of polyamide (PA).
- An array of membranes may be employed.
- the reverse osmosis membrane may be planar or take the form of a tube or hollow fibre.
- a tubular configuration of hollow fine fibre membranes may be used.
- the membrane may be supported on a supporting structure, such as a mesh support.
- a planar membrane When a planar membrane is employed, the sheet may be rolled such that it defines a spiral in cross-section.
- one or more tubular membranes When a tubular membrane is employed, one or more tubular membranes may be contained within a housing or shell.
- the reverse osmosis membrane may be operated at an elevated pressure to drive the (liquid) solution through the membrane.
- the reverse osmosis step may be carried out at a pressure of 25 to 120 bar, preferably 50 to 100 bar, more preferably 60 to 80 bar.
- a scale inhibitor, anti-scaling or anti-fouling additive may be added to any one of the solutions in contact with any of the membranes.
- the scale inhibitor, anti-scaling or anti-fouling additive may be re-circulated between the retentate- side of one membrane and a permeate-side of another or vice-versa.
- FIG. 1 this represents a schematic illustration of a system for carrying out a process according to a first example of the present disclosure.
- the system 10 comprises a reverse osmosis unit 12 comprising a first semi-permeable membrane 14.
- a feed solution 16 is contacted with one side of the membrane 14 and hydraulic pressure is applied so that solvent (e.g. water) from the feed solution 16 flows through the membrane 14 by reverse osmosis to provide a permeate solution 18 on the permeate-side 14b of the first semi-permeable membrane and a residual solution 20 on the feed-side 14a of the first semi-permeable membrane.
- solvent e.g. water
- a portion 16a of the feed solution 16 is fed to the permeate-side 14b of the membrane 14. This can reduce osmotic pressure difference across the membrane 14. As a result, the hydraulic pressure required to induce solvent flow from the feed solution by reverse osmosis may be reduced.
- the residual solution 20 may be removed, for example, as a concentrated waste product, for example, for disposal or further processing or use.
- Figure 2 depicts a schematic illustration of a system for carrying out a process according to a second example of the present disclosure.
- the system 10 of Figure 2 is similar to the system of Figure 1 and like parts have been labelled with like numerals. Unlike the system 10 of Figure 1 , however, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the membrane 14 to reduce the osmotic pressure difference across the membrane 14.
- Figure 3 depicts a schematic illustration of a system for carrying out a process according to a third example of the present disclosure.
- the system 10 of Figure 3 is similar to the system 10 of Figure 1 and like parts have been labelled with like numerals.
- the apparatus of Figure 3 further includes an initial reverse osmosis unit 22 comprising an initial semi-permeable membrane 24.
- a pump 26 is also provided.
- the feed solution 16 is produced by contacting an initial solution 28 with one side of an initial semi-permeable membrane 24.
- hydraulic pressure is applied to the initial solution 28, such that solvent from the initial solution 28 flows through the initial semi-permeable membrane 24 by reverse osmosis to provide an initial permeate solution 30 on the permeate-side of the initial semi-permeable membrane and an initial residual solution 32 on the feed-side of the initial semi-permeable membrane.
- the initial residual solution 32 is employed as the feed solution 16 to the first semi-permeable membrane 14.
- the initial permeate solution 30 may be withdrawn and used or further purified.
- the pump 26 may be used to deliver the hydraulic pressure required for the downstream reverse osmosis units.
- FIG. 4 depicts a schematic illustration of a system for carrying out a process according to a fourth example of the present disclosure.
- the system 10 of Figure 4 is similar to the system of Figure 3 and like parts have been labelled with like numerals. Rather than feeding a portion 16a of the feed solution 16 to the permeate-side 14b of the first semi-permeable membrane 14, however, it is a portion 20a of the residual solution 20 on the feed-side 14a of the first semi-permeable membrane 14 that fed to the permeate- side 14b of the first semi-permeable membrane 14.
- Figure 5 depicts a schematic illustration of a system for carrying out a process according to a fifth example of the present disclosure.
- the system 10 of Figure 5 is similar to the system 10 of Figure 3 and like parts have been labelled with like numerals.
- the residual solution 20 from the feed-side 14a of the first semi-permeable membrane is withdrawn and contacted with one side of a further semi-permeable membrane 34 as a further feed solution.
- Hydraulic pressure delivered by pump 26 or other means is applied to the further feed solution in contact with the further semi-permeable membrane 34, such that solvent from the further feed solution flows through the further semi-permeable membrane 34 by reverse osmosis.
- This provides a further permeate solution 36 on the permeate-side of the further semi-permeable membrane and a further residual solution 38 on the feed-side of the further semi-permeable membrane 34.
- a portion of the further feed solution 20b is fed to the permeate-side of the second semi-permeable membrane.
- the further residual solution 38 may be disposed or concentrated further for disposal. At least a portion of the further permeate solution 36 may be recycled as at least part of the initial solution 28.
- Figure 6 depicts a schematic illustration of a system for carrying out a process according to a sixth example of the present disclosure.
- the system 10 of Figure 6 is similar to the system 10 of Figure 5 and like parts have been labelled with like numerals. However, in Figure 6, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the first semi-permeable membrane 14 to reduce the osmotic difference across the membrane 14. It is also a portion 38a of the further residual solution 38 on the feed-side of the further semi-permeable membrane 34 that is recycled to the permeate-side of the further semi-permeable membrane.
- Figure 7 depicts a schematic illustration of a system for carrying out a process according to a seventh example of the present disclosure.
- the system 10 of Figure 7 is similar to the system 10 of Figure 1 and like parts have been labelled with like numerals.
- the feed solution 16 is produced by contacting an initial solution 100 with one side of an initial semi-permeable membrane 110. Hydraulic pressure may be applied to the initial solution, for example, via pump 112, such that solvent from the initial solution 100 flows through the initial semi-permeable membrane 110 by reverse osmosis to provide an initial residual solution 114 on the feed-side of the initial semi-permeable membrane and an initial permeate solution 116 on the permeate-side of the initial semi- permeable membrane.
- the initial permeate solution 116 may be withdrawn for use or further purification.
- the initial residual solution 114 is contacted with one side of a further semi-permeable membrane 118. Hydraulic pressure may be applied to the initial residual solution 114, for example, using pump 112, such that solvent from the initial residual solution 114 flows through the further semi-permeable membrane 118 by reverse osmosis. This flow of solvent provides a further permeate solution 120 on the permeate-side of the further semi-permeable membrane 118 and a further residual solution 122 on the feed-side of the further semi-permeable membrane 118.
- the further residual solution 122 may be used as a feed to the first semi-permeable membrane 14.
- the permeate solution 18 from the first semi-permeable membrane 14 may be fed to the permeate-side of the further semi-permeable membrane 118.
- the further permeate solution 120 on the permeate-side of the further semi-permeable membrane 118 may be recycled for use as or as part of the initial solution 100.
- Figure 8 depicts a schematic illustration of a system for carrying out a process according to an eighth example of the present disclosure.
- the system 10 of Figure 8 is similar to the system 10 of Figure 7 and like parts have been labelled with like numerals. However, in Figure 6, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the first semi-permeable membrane 14 to reduce the osmotic difference across the membrane 14.
- Figure 9 depicts a schematic illustration of a system for carrying out a process according to a ninth example of the present disclosure.
- the system 10 of Figure 9 is similar to the system 10 of Figure 8 and like parts have been labelled with like numerals.
- the permeate solution 18 from the first semi-permeable membrane 14 is fed to the permeate side of the further semi-permeable membrane 118, it is a portion 20c of the residual solution 20 from the feed-side 14a of the first semi-permeable membrane 14 that is fed to the permeate side of the further semi-permeable membrane 118.
- the permeate solution 18 from the first semi-permeable membrane 14 is recycled for use as part of the initial solution 100.
- Figure 10 depicts a schematic illustration of a system for carrying out a process according to a tenth example of the present disclosure.
- the system 10 of Figure 10 is similar to the system 10 of Figure 9 and like parts have been labelled with like numerals.
- the initial solution 100 is produced by contacting an impure solution 200 with one side of a forward osmosis membrane 210.
- the opposite side of the forward osmosis membrane 210 is contacted with an initial solution precursor 212, wherein the solute concentration of the initial solution precursor 212 is higher than the solute concentration of the impure solution such that solvent from the impure solution flows across the forward osmosis membrane by forward osmosis to dilute the initial solution precursor to produce the initial solution 100.
- the initial solution 100 may be stored, for example, in storage vessel 216 prior to contact with the initial semi-permeable membrane 110.
- the concentrated impure solution 214 on the feed-side of the forward osmosis membrane 210 may be withdrawn and optionally discarded or further concentrated.
- the initial solution precursor 212 may be formed by dissolving osmotic agent 218 in water.
- the initial solution precursor 212 may be formed from by recycling at least a portion of the residual solution 20 from the first semi-permeable membrane 14 to the permeate-side of the forward osmosis membrane 210. If desired, a bleed of the recycled residual solution 20 may be removed and discarded via line 220.
- FIG. 11 depicts a schematic illustration of a system for carrying out a process according to an eleventh example of the present disclosure.
- hydraulic pressure is applied using a pump to drive an initial feed 300 through a reverse osmosis membrane 310 under reverse osmosis conditions.
- the permeate 312 is withdrawn as product, while the residual solution 314 is contacted with a semi-permeable membrane 316. Residual pressure from the pump is used to drive the residual solution through the membrane.
- a draw solution 318 containing added osmotic agent 328 is contacted with the opposite side of the semi-permeable membrane 316 so as to reduce the osmotic pressure differential across the membrane 316. This osmotically assists the reverse osmosis step across the membrane 316.
- the permeate through the membrane 316 is withdrawn as dilute draw solution and stored in tank 322, while the residual solution 324 from membrane 316 is withdrawn as concentrate.
- a portion of the draw solution is withdrawn and pumped 325 through a reverse osmosis membrane 326. This generates a permeate 328 that can be withdrawn as product, and a residual solution 330.
- the residual solution 330 is contacted with a semi-permeable membrane 332. Pressure applied using the pump 325 for the preceding reverse osmosis step may be used to drive the residual solution 330 through membrane 332 to produce a permeate, which is recycled to tank 322.
- a portion 336 of the residual solution 334 is fed to the permeate side of the membrane 332 to osmotically assist reverse osmosis across membrane 332.
- the remainder of the residual solution 334 is recycled as regenerated draw solution to the membrane 316.
- Osmotic agent 328 may be added to the regenerated draw solution.
- a bleed 338 may also may be used to withdraw some of the regenerated draw solution, for example, as a bleed for disposal or treatment e.g. to reduce the risk of build-up of unwanted impurities within the circulating draw solution.
Abstract
A process for separating solvent from a feed solution, said process comprising contacting the feed solution with one side of a first semi-permeable membrane; applying hydraulic pressure to the feed solution, such that solvent from the feed solution flows through the first semi-permeable membrane by reverse osmosis to provide a permeate solution on the permeate-side of the first semi-permeable membrane and a residual solution on the feed-side of the first semi-permeable membrane; and feeding a portion of the feed solution or a portion of the residual solution to the permeate- side of the first semi-permeable membrane.
Description
Solvent Separation
Background
[0001] The present invention relates to a process for separating a solvent, for example, water from a feed solution.
[0002] In water purification methods, water is separated from an impure solution, for example, a saline solution. Various methods of water purification are known. An example of such a method is reverse osmosis. In reverse osmosis, water is forced from a region of high solute concentration through a semipermeable membrane to a region of low solute concentration by applying a hydraulic pressure in excess of the osmotic pressure of the high solute concentration solution. Reverse osmosis is commonly used, for example, to obtain drinking water from seawater. Reverse osmosis is also used to separate water from, for example, industrial waste streams. By using reverse osmosis to treat industrial waste streams, it is possible to generate relatively clean water from industrial waste, while reducing the volume of undesirable waste requiring disposal or further treatment.
[0003] Reverse osmosis requires relatively high pressures to be exerted on the high solute concentration side of the membrane. For instance, to desalinate seawater by conventional reverse osmosis techniques, pressures as high as 82 barg are commonly used to increase the recovery of product water. This places a significant energy burden on desalination methods that rely on conventional reverse osmosis. Moreover, streams having higher solute concentrations than seawater may require even higher hydraulic pressures to be applied. Many commercially available reverse osmosis membranes are unsuitable for withstanding hydraulic pressures of greater than 82 barg. Accordingly, this can impose a limitation on the concentration of feed solutions that can be treated using commercially available reverse osmosis membrane, which effectively limits the maximum concentration of the concentrated feed stream to an osmotic pressure equivalent to the maximum hydraulic pressure rating of the reverse osmosis membrane and pressure vessel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:
Figure 1 is a schematic illustration of a system for carrying out a process according to a first example of the present disclosure;
Figure 2 is a schematic illustration of a system for carrying out a process according to a second example of the present disclosure;
Figure 3 is a schematic illustration of a system for carrying out a process according to a third example of the present disclosure;
Figure 4 is a schematic illustration of a system for carrying out a process according to a fourth example of the present disclosure;
Figure 5 is a schematic illustration of a system for carrying out a process according to a fifth example of the present disclosure;
Figure 6 is a schematic illustration of a system for carrying out a process according to a sixth example of the present disclosure;
Figure 7 is a schematic illustration of a system for carrying out a process according to a seventh example of the present disclosure;
Figure 8 is a schematic illustration of a system for carrying out a process according to an eighth example of the present disclosure;
Figure 9 is a schematic illustration of a system for carrying out a process according to a ninth example of the present disclosure;
Figure 10 is a schematic illustration of a system for carrying out a process according to a tenth example of the present disclosure; and
Figure 11 is a schematic illustration of a system for carrying out a process according to an eleventh example of the present disclosure
DETAILED DESCRIPTION
[0005] Throughout the description and claims of this specification, the words“comprise” and“contain” and variations of them mean“including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
[0006] Features, integers, characteristics, and compounds in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any
accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0007] According to the present invention, there is provided a process for separating solvent from a feed solution, said process comprising:
[0008] contacting the feed solution with one side of a first semi-permeable membrane;
[0009] applying hydraulic pressure to the feed solution, such that solvent from the feed solution flows through the first semi-permeable membrane by reverse osmosis to provide a permeate solution on the permeate-side of the first semi-permeable membrane and a residual solution on the feed-side of the first semi-permeable membrane; and
[0010] feeding a portion of the feed solution or a portion of the residual solution to the permeate-side of the first semi-permeable membrane.
[0011] Preferably, the solvent is water. The feed solution may be a salt solution, for example, a saline solution. The feed solution may be an impure water stream, for example, saline ground water or surface water, brine and seawater. Other examples include waste water streams, lake water, river water and pond water. Examples of waste water streams include industrial or agricultural waste water streams. Alternatively, the feed solution may be a salt solution that is prepared by dissolving an osmotic agent in water.
[0012] The present inventors have found that, by feeding a portion of the feed solution or a portion of the residual solution to the permeate-side of the first semi-permeable membrane, the osmotic pressure difference across the first semi-permeable membrane may be reduced. As a result, the hydraulic pressure required to induce solvent flow from the feed solution by reverse osmosis may be reduced. The reverse osmosis step, therefore, can become osmotically assisted (i.e. osmotically assisted reverse osmosis or “OARO”). Accordingly, the flux across the semi-permeable membrane is higher compared to that achievable using reverse osmosis alone operating under the same hydraulic pressure limitations. In other words, to achieve the same level of flux across the semi- permeable membrane, lower hydraulic pressures may be employed. An important advantage of the present invention is that it allows highly concentrated feed solutions to be treated at hydraulic pressures that are within the hydraulic pressure ratings of conventional
reverse osmosis membranes (e.g.82 barg or less). With conventional reverse osmosis techniques, such highly concentrated feed solutions would require hydraulic pressures in excess of the maximum hydraulic pressure rating of most conventional reverse osmosis membranes (e.g. above 82 barg).
[0013] In one embodiment, it is a portion of the feed solution that is fed to the permeate- side of the first semi-permeable membrane.
[0014] Alternatively or additionally, it is a portion of the residual solution that is fed to the permeate-side of the first semi-permeable membrane. Making use of a portion of the residual solution to feed to the permeate-side of the first semi-permeable membrane may be advantageous because of the concentrated nature of the residual solution. A lower flow of residual solution to the permeate-side of the first semi-permeable membrane may be required in comparison to a flow of feed solution, for example, in order to provide the same brine concentration. This may result from the higher osmotic pressure of the residual solution. In addition, a more concentrated residual solution may be obtained for a given hydraulic pressure. In one embodiment, where the first semi-permeable membrane is a hollow fibre membrane and wherein the draw solution is on the fibre bore, feeding a portion of the residual solution may be more energy efficient than feeding, for example, a portion of the feed solution. The lower pressure drop down the fibre bore may mean than less energy is required.
[0015] Preferably, the feed solution to the first semi-permeable membrane may be produced by contacting an initial solution with one side of an initial semi-permeable membrane. Hydraulic pressure may be applied to the initial solution, such that solvent from the initial solution can flow through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi- permeable membrane and an initial residual solution on the feed-side of the initial semi- permeable membrane. The initial residual solution may be employed as the feed solution to the first semi-permeable membrane. The initial permeate solution may be withdrawn, for example, for use or further purification. Withdrawing the initial permeate solution for use after the initial reverse osmosis stage may advantageously produce a higher quality permeate, in comparison to feeding the initial permeate solution to further reverse osmosis steps. This may result from the lower concentration in the feed/concentrate side of the initial semi-permeable membrane. Additionally, the inclusion of an initial reverse osmosis step may provide economic benefits, as conventional, widely used reverse osmosis may be employed. In one embodiment, a portion of the permeate solution on the permeate side of the first semi-permeable membrane may be recycled as a feed to the initial semi- permeable membrane.
[0016] In one embodiment, the hydraulic pressure applied to the initial solution may be used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane. For example, a pump may be used to apply hydraulic pressure to drive the initial solution through the initial semi-permeable membrane. This hydraulic pressure may also be used fully or in part to drive downstream membrane separation steps.
[0017] In one embodiment, the process further comprises withdrawing at least a portion of the residual solution on the feed-side of the first semi-permeable membrane and contacting the withdrawn solution with one side of a further semi-permeable membrane as a further feed solution. Hydraulic pressure may be applied to the further feed solution in contact with the further semi-permeable membrane to cause solvent from the further feed solution to flow through the further semi-permeable membrane by reverse osmosis to provide a further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane. A portion of the further feed solution or a portion of the further residual solution may be fed to the permeate-side of the further semi-permeable membrane. As explained above, this can reduce the osmotic pressure difference across the further semi- permeable membrane. The hydraulic pressure required to induce solvent flow from the further feed solution by reverse osmosis may hence be reduced.
[0018] While hydraulic pressure may be applied using a dedicated pump, it is possible to use a pump employed to apply hydraulic pressure to the initial solution in an initial reverse osmosis step to apply hydraulic pressure for one or more of any subsequent osmotically assisted reverse osmosis steps.
[0019] In some embodiments, a series of further semi-permeable membranes may be provided downstream of the first semi-permeable membrane. The residual solution from any one of these membranes may be withdrawn and contacted with a downstream membrane as a feed solution for the downstream membrane. A portion of the feed solution to the downstream membrane or a portion of the residual solution on the feed-side of the downstream membrane may be fed to the permeate-side of the downstream membrane.
[0020] Where the process includes the use of an initial semi-permeable membrane as described above, a portion of the further permeate solution on the permeate side of the further semi-permeable membrane may be recycled as or as part of a feed to the initial semi-permeable membrane.
[0021] In another embodiment, the feed solution to the first semi-permeable membrane is produced by contacting an initial solution with one side of an initial semi-permeable membrane. Hydraulic pressure may be applied to the initial solution, such that solvent
from the initial solution flows through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi- permeable membrane and an initial residual solution on the feed-side of the initial semi- permeable membrane. The initial residual solution may then be contacted with one side of a further semi-permeable membrane. Hydraulic pressure may be applied to the initial residual solution, such that solvent from the initial residual solution flows through the further semi-permeable membrane by reverse osmosis to provide a further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane. The further residual solution may then be used as the feed to the first semi-permeable membrane.
[0022] In some embodiments, the initial residual solution may flow through a series of further semi-permeable membranes, each producing its respective permeate and residual solutions. At least one of these residual solutions may be used as the feed to the first semi-permeable membrane.
[0023] In some embodiments, at least a portion of the further residual solution from the (or one of the) further semi-permeable membrane is withdrawn and fed to the permeate- side of the first semi-permeable membrane.
[0024] In some embodiments, at least a portion of the first permeate solution from the first semi-permeable membrane is recycled as a feed to the initial semi-permeable membrane.
[0025] In some embodiments, the hydraulic pressure applied to the initial solution is used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane and/or the further feed solution that is contacted with the or at least one of the further semi-permeable membranes.
[0026] The feed solution and/or the initial solution may be any solution, such as an aqueous solution. The feed solution and/or the initial solution may be a salt solution, for example, an aqueous salt solution. In some embodiments, the feed solution and/or the initial solution may contain a plurality of dissolved salts. In some embodiments, the feed solution and/or the initial solution is an aqueous solution of sodium chloride. Examples of suitable feed solutions and/or the initial solutions include saline ground water or surface water, brine and seawater. Other examples include waste water streams, lake water, river water and pond water. Examples of waste water streams include industrial or agricultural waste water streams.
[0027] The feed solution and/or the initial solution may be a solution of one or more osmotic agents. Suitable osmotic agents include salts, such as inorganic salts. Suitable
salts include salts of ammonium and metals, such as alkali metals (e.g. Li, Na, K) and alkali earth metals (e.g. Mg and Ca). The salts may be fluorides, chlorides, bromides, iodides, sulphates, sulphites, sulphides, carbonates, hydrogencarbonates, nitrates, nitrites, nitrides, phosphates, aluminates, borates, bromates, carbides, chlorides, perchlorates, hypochlorates, chromates, fluorosilicates, fluorosulphates, silicates, cyanides and cyanates. One or more salts may be present. An example may be sodium chloride.
[0028] The total dissolved salt concentration of the feed solution and/or the initial solution may be at least 5,000 mg/I, for example, 5,000 to 250,000 mg/I. In one example, the total dissolved salt concentration of the feed solution and/or the initial solution to the first semi- permeable membrane is at least 30,000 mg/I. The osmotic pressure of the feed may be at least 4 barg, for example, 4 to 320 barg.
[0029] In some examples, the initial solution may be produced by contacting an impure solution with one side of a forward osmosis membrane, and contacting the opposite side of the forward osmosis membrane with an initial solution precursor. The osmotic pressure (solute concentration) of the initial solution precursor may be higher than the osmotic pressure (solute concentration) of the impure solution such that solvent from the impure solution flows across the forward osmosis membrane by forward osmosis to dilute the initial solution precursor to produce the initial solution.
[0030] The impure solution may be saline ground water or surface water, brine and seawater. Other examples include waste water streams, lake water, river water and pond water. Examples of waste water streams include industrial or agricultural waste water streams.
[0031] The initial solution and/or initial solution precursor may be formed by dissolving an osmotic agent in a solvent, for example, water.
[0032] Suitable osmotic agents include salts, such as sodium chloride. Other examples of salts include salts of ammonium and metals, such as alkali metals (e.g. Li, Na, K) and alkali earth metals (e.g. Mg and Ca). The salts may be fluorides, chlorides, bromides, iodides, sulphates, sulphites, sulphides, carbonates, hydrogencarbonates, nitrates, nitrites, nitrides, phosphates, aluminates, borates, bromates, carbides, chlorides, perchlorates, hypochlorates, chromates, fluorosilicates, fluorosulphates, silicates, cyanides and cyanates. One or more salts may be employed.
[0033] The semi-permeable membrane(s) employed in the present invention may be nanofiltration or reverse osmosis membranes. Preferably, the semi-permeable membrane is a reverse osmosis membrane. Where more than two membranes are employed, the membranes may be the same or different. In one embodiment, the semi-permeable
membrane(s) are all reverse osmosis membranes. In another embodiment, the semi- permeable membrane(s) are all nanofiltration membranes. In yet another embodiment, both nanofiltration and reverse osmosis membranes are employed as the semi-permeable membrane(s).
[0034] Any suitable reverse osmosis membrane may be used in the present invention. For example, the reverse osmosis membrane may have an average (e.g. mean) pore size of 0.5 to 80 Angstroms, preferably, 2 to 50 Angstroms. In a preferred embodiment, the membrane has an average (e.g. mean) pore size of from 3 to 30 Angstroms. Pore size (e.g. mean pore size) may be measured using any suitable technique. For example, a differential flow method may be employed (Japan Membrane Journal, vol. 29; no. 4; pp. 227 -235 (2004)) or the use of salts, uncharged solutes and atomic force microscopy (Journal of Membrane Science 126 (1997) 91-105).
[0035] Suitable reverse osmosis membranes include integral membranes and composite membranes. Specific examples of suitable membranes include membranes formed of cellulose acetate (CA) and/or cellulose triacetate (CTA) , such as or similar to those used in the study of McCutcheon et al . Desalination 174 (2005) 1-11 and membranes formed of polyamide (PA). An array of membranes may be employed.
[0036] The reverse osmosis membrane may be planar or take the form of a tube or hollow fibre. For example, a tubular configuration of hollow fine fibre membranes may be used. If desired, the membrane may be supported on a supporting structure, such as a mesh support. When a planar membrane is employed, the sheet may be rolled such that it defines a spiral in cross-section. When a tubular membrane is employed, one or more tubular membranes may be contained within a housing or shell.
[0037] The reverse osmosis membrane may be operated at an elevated pressure to drive the (liquid) solution through the membrane. For example, the reverse osmosis step may be carried out at a pressure of 25 to 120 bar, preferably 50 to 100 bar, more preferably 60 to 80 bar.
[0038] Optionally, a scale inhibitor, anti-scaling or anti-fouling additive may be added to any one of the solutions in contact with any of the membranes. Preferably, the scale inhibitor, anti-scaling or anti-fouling additive may be re-circulated between the retentate- side of one membrane and a permeate-side of another or vice-versa.
[0039] These and other aspects of the present invention will now be described with reference to the accompanying figures. Referring to Figure 1 , this represents a schematic illustration of a system for carrying out a process according to a first example of the present disclosure. The system 10 comprises a reverse osmosis unit 12 comprising a first
semi-permeable membrane 14. A feed solution 16 is contacted with one side of the membrane 14 and hydraulic pressure is applied so that solvent (e.g. water) from the feed solution 16 flows through the membrane 14 by reverse osmosis to provide a permeate solution 18 on the permeate-side 14b of the first semi-permeable membrane and a residual solution 20 on the feed-side 14a of the first semi-permeable membrane. A portion 16a of the feed solution 16 is fed to the permeate-side 14b of the membrane 14. This can reduce osmotic pressure difference across the membrane 14. As a result, the hydraulic pressure required to induce solvent flow from the feed solution by reverse osmosis may be reduced.
[0040] The residual solution 20 may be removed, for example, as a concentrated waste product, for example, for disposal or further processing or use.
[0041] Figure 2 depicts a schematic illustration of a system for carrying out a process according to a second example of the present disclosure. The system 10 of Figure 2 is similar to the system of Figure 1 and like parts have been labelled with like numerals. Unlike the system 10 of Figure 1 , however, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the membrane 14 to reduce the osmotic pressure difference across the membrane 14.
[0042] Figure 3 depicts a schematic illustration of a system for carrying out a process according to a third example of the present disclosure. The system 10 of Figure 3 is similar to the system 10 of Figure 1 and like parts have been labelled with like numerals. However, the apparatus of Figure 3 further includes an initial reverse osmosis unit 22 comprising an initial semi-permeable membrane 24. A pump 26 is also provided.
[0043] When operating the process using the system 10 of Figure 3, the feed solution 16 is produced by contacting an initial solution 28 with one side of an initial semi-permeable membrane 24. Using pump 26, hydraulic pressure is applied to the initial solution 28, such that solvent from the initial solution 28 flows through the initial semi-permeable membrane 24 by reverse osmosis to provide an initial permeate solution 30 on the permeate-side of the initial semi-permeable membrane and an initial residual solution 32 on the feed-side of the initial semi-permeable membrane. The initial residual solution 32 is employed as the feed solution 16 to the first semi-permeable membrane 14. The initial permeate solution 30 may be withdrawn and used or further purified. The pump 26 may be used to deliver the hydraulic pressure required for the downstream reverse osmosis units.
[0044] The permeate solution 18 on the permeate-side of the first semi-permeable membrane 14 may be recycled for use as part of the initial solution 28.
[0045] Figure 4 depicts a schematic illustration of a system for carrying out a process according to a fourth example of the present disclosure. The system 10 of Figure 4 is similar to the system of Figure 3 and like parts have been labelled with like numerals. Rather than feeding a portion 16a of the feed solution 16 to the permeate-side 14b of the first semi-permeable membrane 14, however, it is a portion 20a of the residual solution 20 on the feed-side 14a of the first semi-permeable membrane 14 that fed to the permeate- side 14b of the first semi-permeable membrane 14.
[0046] Figure 5 depicts a schematic illustration of a system for carrying out a process according to a fifth example of the present disclosure. The system 10 of Figure 5 is similar to the system 10 of Figure 3 and like parts have been labelled with like numerals.
However, in the system 10 of Figure 5, the residual solution 20 from the feed-side 14a of the first semi-permeable membrane is withdrawn and contacted with one side of a further semi-permeable membrane 34 as a further feed solution.
[0047] Hydraulic pressure delivered by pump 26 or other means is applied to the further feed solution in contact with the further semi-permeable membrane 34, such that solvent from the further feed solution flows through the further semi-permeable membrane 34 by reverse osmosis. This provides a further permeate solution 36 on the permeate-side of the further semi-permeable membrane and a further residual solution 38 on the feed-side of the further semi-permeable membrane 34. A portion of the further feed solution 20b is fed to the permeate-side of the second semi-permeable membrane. The further residual solution 38 may be disposed or concentrated further for disposal. At least a portion of the further permeate solution 36 may be recycled as at least part of the initial solution 28.
[0048] Figure 6 depicts a schematic illustration of a system for carrying out a process according to a sixth example of the present disclosure. The system 10 of Figure 6 is similar to the system 10 of Figure 5 and like parts have been labelled with like numerals. However, in Figure 6, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the first semi-permeable membrane 14 to reduce the osmotic difference across the membrane 14. It is also a portion 38a of the further residual solution 38 on the feed-side of the further semi-permeable membrane 34 that is recycled to the permeate-side of the further semi-permeable membrane.
[0049] Figure 7 depicts a schematic illustration of a system for carrying out a process according to a seventh example of the present disclosure. The system 10 of Figure 7 is similar to the system 10 of Figure 1 and like parts have been labelled with like numerals. However, in Figure 7, the feed solution 16 is produced by contacting an initial solution 100 with one side of an initial semi-permeable membrane 110. Hydraulic pressure may be applied to the initial solution, for example, via pump 112, such that solvent from the initial
solution 100 flows through the initial semi-permeable membrane 110 by reverse osmosis to provide an initial residual solution 114 on the feed-side of the initial semi-permeable membrane and an initial permeate solution 116 on the permeate-side of the initial semi- permeable membrane. The initial permeate solution 116 may be withdrawn for use or further purification. The initial residual solution 114 is contacted with one side of a further semi-permeable membrane 118. Hydraulic pressure may be applied to the initial residual solution 114, for example, using pump 112, such that solvent from the initial residual solution 114 flows through the further semi-permeable membrane 118 by reverse osmosis. This flow of solvent provides a further permeate solution 120 on the permeate-side of the further semi-permeable membrane 118 and a further residual solution 122 on the feed-side of the further semi-permeable membrane 118. The further residual solution 122 may be used as a feed to the first semi-permeable membrane 14.
[0050] The permeate solution 18 from the first semi-permeable membrane 14 may be fed to the permeate-side of the further semi-permeable membrane 118. The further permeate solution 120 on the permeate-side of the further semi-permeable membrane 118 may be recycled for use as or as part of the initial solution 100.
[0051] Figure 8 depicts a schematic illustration of a system for carrying out a process according to an eighth example of the present disclosure. The system 10 of Figure 8 is similar to the system 10 of Figure 7 and like parts have been labelled with like numerals. However, in Figure 6, it is a portion 20a of the residual solution 20 that is recycled to the permeate-side 14b of the first semi-permeable membrane 14 to reduce the osmotic difference across the membrane 14.
[0052] Figure 9 depicts a schematic illustration of a system for carrying out a process according to a ninth example of the present disclosure. The system 10 of Figure 9 is similar to the system 10 of Figure 8 and like parts have been labelled with like numerals. However, instead of the permeate solution 18 from the first semi-permeable membrane 14 being fed to the permeate side of the further semi-permeable membrane 118, it is a portion 20c of the residual solution 20 from the feed-side 14a of the first semi-permeable membrane 14 that is fed to the permeate side of the further semi-permeable membrane 118. The permeate solution 18 from the first semi-permeable membrane 14 is recycled for use as part of the initial solution 100.
[0053] Figure 10 depicts a schematic illustration of a system for carrying out a process according to a tenth example of the present disclosure. The system 10 of Figure 10 is similar to the system 10 of Figure 9 and like parts have been labelled with like numerals. However, in Figure 10, the initial solution 100 is produced by contacting an impure solution 200 with one side of a forward osmosis membrane 210. The opposite side of the forward
osmosis membrane 210 is contacted with an initial solution precursor 212, wherein the solute concentration of the initial solution precursor 212 is higher than the solute concentration of the impure solution such that solvent from the impure solution flows across the forward osmosis membrane by forward osmosis to dilute the initial solution precursor to produce the initial solution 100. The initial solution 100 may be stored, for example, in storage vessel 216 prior to contact with the initial semi-permeable membrane 110. The concentrated impure solution 214 on the feed-side of the forward osmosis membrane 210 may be withdrawn and optionally discarded or further concentrated.
[0054] The initial solution precursor 212 may be formed by dissolving osmotic agent 218 in water. The initial solution precursor 212 may be formed from by recycling at least a portion of the residual solution 20 from the first semi-permeable membrane 14 to the permeate-side of the forward osmosis membrane 210. If desired, a bleed of the recycled residual solution 20 may be removed and discarded via line 220.
[0055] Figure 11 depicts a schematic illustration of a system for carrying out a process according to an eleventh example of the present disclosure. In Figure 11 , hydraulic pressure is applied using a pump to drive an initial feed 300 through a reverse osmosis membrane 310 under reverse osmosis conditions. The permeate 312 is withdrawn as product, while the residual solution 314 is contacted with a semi-permeable membrane 316. Residual pressure from the pump is used to drive the residual solution through the membrane. However, a draw solution 318 containing added osmotic agent 328 is contacted with the opposite side of the semi-permeable membrane 316 so as to reduce the osmotic pressure differential across the membrane 316. This osmotically assists the reverse osmosis step across the membrane 316. The permeate through the membrane 316 is withdrawn as dilute draw solution and stored in tank 322, while the residual solution 324 from membrane 316 is withdrawn as concentrate.
[0056] To regenerate the diluted draw solution in tank 322, a portion of the draw solution is withdrawn and pumped 325 through a reverse osmosis membrane 326. This generates a permeate 328 that can be withdrawn as product, and a residual solution 330. The residual solution 330 is contacted with a semi-permeable membrane 332. Pressure applied using the pump 325 for the preceding reverse osmosis step may be used to drive the residual solution 330 through membrane 332 to produce a permeate, which is recycled to tank 322. A portion 336 of the residual solution 334, however, is fed to the permeate side of the membrane 332 to osmotically assist reverse osmosis across membrane 332. The remainder of the residual solution 334 is recycled as regenerated draw solution to the membrane 316. Osmotic agent 328 may be added to the regenerated draw solution. A bleed 338 may also may be used to withdraw some of the regenerated draw solution, for
example, as a bleed for disposal or treatment e.g. to reduce the risk of build-up of unwanted impurities within the circulating draw solution.
[0057] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
Claims
1. A process for separating solvent from a feed solution, said process comprising contacting the feed solution with one side of a first semi-permeable membrane;
applying hydraulic pressure to the feed solution, such that solvent from the feed solution flows through the first semi-permeable membrane by reverse osmosis to provide a permeate solution on the permeate-side of the first semi-permeable membrane and a residual solution on the feed-side of the first semi-permeable membrane; and
feeding a portion of the feed solution or a portion of the residual solution to the permeate-side of the first semi-permeable membrane.
2. A process as claimed in claim 1 , wherein it is a portion of the feed solution that is fed to the permeate-side of the first semi-permeable membrane.
3. A process as claimed in claim 1 , wherein it is a portion of the residual solution that is fed to the permeate-side of the first semi-permeable membrane.
4. A process as claimed in any one of the preceding claims, wherein the feed solution to the first semi-permeable membrane is produced by contacting an initial solution with one side of an initial semi-permeable membrane; applying hydraulic pressure to the initial solution, such that solvent from the initial solution flows through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi-permeable membrane and an initial residual solution on the feed-side of the initial semi-permeable membrane; wherein the initial residual solution is employed as the feed solution.
5. A process as claimed in claim 4, wherein a portion of the permeate solution on the permeate side of the first semi-permeable membrane is recycled as a feed to the initial semi-permeable membrane.
6. A process as claimed in claim 4 or 5, wherein the hydraulic pressure applied to the initial solution is used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane.
7. A process as claimed in any one of claims 4 to 6, which further comprises withdrawing at least a portion of the residual solution from the feed-side of the first semi-permeable membrane and contacting the withdrawn solution with one side of a further semi-permeable membrane as a further feed solution.
8. A process as claimed in claim 7, which further comprises applying hydraulic
pressure to the further feed solution in contact with the further semi-permeable membrane, such that solvent from the further feed solution flows through the further semi-permeable membrane by reverse osmosis to provide a further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane; and
feeding a portion of the further feed solution or a portion of the further residual solution to the permeate-side of the second semi-permeable membrane.
9. A process as claimed in claim 8, wherein a portion of the further permeate solution on the permeate side of the further semi-permeable membrane is recycled as a feed to the initial semi-permeable membrane.
10. A process as claimed in any one of claims 7 to 9, wherein the hydraulic pressure applied to the initial solution is used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane and the feed solution that is contacted with the further semi-permeable membrane.
11. A process as claimed in claim 1 , wherein the feed solution to the first semi- permeable membrane is produced by
contacting an initial solution with one side of an initial semi-permeable membrane;
applying hydraulic pressure to the initial solution, such that solvent from the initial solution flows through the initial semi-permeable membrane by reverse osmosis to provide an initial permeate solution on the permeate-side of the initial semi-permeable membrane and an initial residual solution on the feed-side of the initial semi-permeable membrane;
contacting the initial residual solution with one side of a further semi- permeable membrane;
applying hydraulic pressure to the initial residual solution, such that solvent from the initial residual solution flows through the further semi-permeable
membrane by reverse osmosis to provide an further permeate solution on the permeate-side of the further semi-permeable membrane and a further residual solution on the feed-side of the further semi-permeable membrane; and
using the further residual solution as the feed to the first semi-permeable membrane.
12. A process as claimed in claim 11 , wherein at least a portion of the first permeate solution from the first semi-permeable membrane is withdrawn and fed to the permeate-side of the further semi-permeable membrane.
13. A process as claimed in claim 11 , wherein at least a portion of the further residual solution from the further semi-permeable membrane is withdrawn and fed to the permeate-side of the first semi-permeable membrane.
14. A process as claimed in claim 11 or 13, wherein at least a portion of the first
permeate solution from the first semi-permeable membrane is recycled as a feed to the initial semi-permeable membrane.
15. A process as claimed in any one of claims 11 to 13, wherein the hydraulic pressure applied to the initial solution is used at least in part to apply hydraulic pressure to the feed solution that is contacted with the first semi-permeable membrane and/or the further feed solution that is contacted with the further semi-permeable membrane.
16. A process as claimed in any one of claims 4 to 15, wherein the initial solution is produced by
contacting an impure solution with one side of a forward osmosis membrane,
contacting the opposite side of the forward osmosis membrane with an initial solution precursor, wherein the osmotic potential of the initial solution precursor is lower than the osmotic potential of the impure solution such that solvent from the impure solution flows across the forward osmosis membrane by forward osmosis to dilute the initial solution precursor to produce the initial solution.
17. A process as claimed in claim 16, wherein a portion of residual solution from the first or further selective membrane is recycled to the opposite side of the forward osmosis membrane.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201880081420.3A CN111867705A (en) | 2017-11-20 | 2018-11-19 | Solvent separation |
ZA2020/03213A ZA202003213B (en) | 2017-11-20 | 2020-05-28 | Solvent separation |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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GB1719153.7 | 2017-11-20 | ||
GBGB1719153.7A GB201719153D0 (en) | 2017-11-20 | 2017-11-20 | Solvent separation |
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WO2019097261A1 true WO2019097261A1 (en) | 2019-05-23 |
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Family Applications (1)
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PCT/GB2018/053347 WO2019097261A1 (en) | 2017-11-20 | 2018-11-19 | Solvent separation |
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CN (1) | CN111867705A (en) |
GB (1) | GB201719153D0 (en) |
WO (1) | WO2019097261A1 (en) |
ZA (1) | ZA202003213B (en) |
Cited By (5)
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US10518221B2 (en) | 2015-07-29 | 2019-12-31 | Gradiant Corporation | Osmotic desalination methods and associated systems |
WO2021061343A1 (en) * | 2019-09-25 | 2021-04-01 | Veolia Water Solutions & Technologies Support | Energy efficient process for concentrating and recovering lithium from a lithium containing brine |
US11629072B2 (en) | 2018-08-22 | 2023-04-18 | Gradiant Corporation | Liquid solution concentration system comprising isolated subsystem and related methods |
US11667549B2 (en) | 2020-11-17 | 2023-06-06 | Gradiant Corporation | Osmotic methods and systems involving energy recovery |
EP4173694A4 (en) * | 2020-06-30 | 2024-04-03 | Toyobo Mc Corp | Membrane separation device and concentrating method |
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WO2016057764A1 (en) * | 2014-10-10 | 2016-04-14 | Oasys Water, Inc. | Osmotic separation systems and methods |
GB201501684D0 (en) * | 2015-02-02 | 2015-03-18 | Surrey Aquatechnology Ltd | Brine Concentration |
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- 2017-11-20 GB GBGB1719153.7A patent/GB201719153D0/en not_active Ceased
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2018
- 2018-11-19 CN CN201880081420.3A patent/CN111867705A/en active Pending
- 2018-11-19 WO PCT/GB2018/053347 patent/WO2019097261A1/en active Application Filing
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2020
- 2020-05-28 ZA ZA2020/03213A patent/ZA202003213B/en unknown
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US20100294718A1 (en) * | 2007-06-08 | 2010-11-25 | Swiss Fresh Water Sa | Liquid purification system using a medium pressure membrane |
US20100032377A1 (en) * | 2008-06-13 | 2010-02-11 | Calvin Wade Wohlert | Apparatus and methods for solution processing using reverse osmosis |
WO2010052651A1 (en) * | 2008-11-04 | 2010-05-14 | Swiss Fresh Water Sa | System for saving energy by recycling concentrate |
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US11400416B2 (en) | 2015-07-29 | 2022-08-02 | Gradiant Corporation | Osmotic desalination methods and associated systems |
US11629072B2 (en) | 2018-08-22 | 2023-04-18 | Gradiant Corporation | Liquid solution concentration system comprising isolated subsystem and related methods |
WO2021061343A1 (en) * | 2019-09-25 | 2021-04-01 | Veolia Water Solutions & Technologies Support | Energy efficient process for concentrating and recovering lithium from a lithium containing brine |
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Also Published As
Publication number | Publication date |
---|---|
GB201719153D0 (en) | 2018-01-03 |
ZA202003213B (en) | 2023-11-29 |
CN111867705A (en) | 2020-10-30 |
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