WO2015111033A1 - Systèmes et procédés de récupération thermique de solutés d'extraction - Google Patents

Systèmes et procédés de récupération thermique de solutés d'extraction Download PDF

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Publication number
WO2015111033A1
WO2015111033A1 PCT/IB2015/051179 IB2015051179W WO2015111033A1 WO 2015111033 A1 WO2015111033 A1 WO 2015111033A1 IB 2015051179 W IB2015051179 W IB 2015051179W WO 2015111033 A1 WO2015111033 A1 WO 2015111033A1
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WO
WIPO (PCT)
Prior art keywords
solutes
draw
heat
sweep gas
gas
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PCT/IB2015/051179
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English (en)
Inventor
Robert Mcginnis
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Nagare Membranes, Llc
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Publication of WO2015111033A1 publication Critical patent/WO2015111033A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/007—Energy recuperation; Heat pumps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/14—Evaporating with heated gases or vapours or liquids in contact with the liquid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
    • B01D3/343—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances the substance being a gas
    • B01D3/346—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances the substance being a gas the gas being used for removing vapours, e.g. transport gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
    • 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
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/406—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • 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
    • B01D2311/06—Specific process operations in the permeate stream
    • 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
    • B01D2311/13—Use of sweep gas
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/22—Cooling or heating elements
    • B01D2313/221—Heat exchangers
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Definitions

  • the present invention relates generally to the use of sweep gas in a falling film heat exchanger for the recovery of volatile solutes within an osmotically driven membrane process. It further relates to the use of heat to compress a sweep gas to induce its flow in such a device.
  • thermal desalination methods additionally employ advanced heat recovery methods, such as multi-effect staging, and the use of heat pumps, either using an external heat transfer fluid, or by compression of the vaporized solvent itself (e.g., mechanical vapor compression (MVC)).
  • MVC mechanical vapor compression
  • draw solutes for example, ammonia and carbon dioxide
  • draw solutes are not separable using current state of the art without some coincident vaporization of solvent during the thermal stripping process.
  • the energy input for solute stripping is higher than it would be in an ideal separation of draw solutes.
  • This additionally causes the vapor stream to contain a mixture of gases and water vapor, the composition of which may affect the condensation temperature and total and practical energy recoverable from this vapor stream.
  • the various embodiments provide a method of recycling draw solutes in an osmotically driven membrane process comprising heating a draw solution comprising dissolved draw solutes and a solvent to increase one or more vapor pressures of the draw solutes, stripping volatile solutes from the solvent by exposing the draw solution to a sweep gas, cooling the sweep gas and stripped volatile solutes such that the volatile solutes become dissolved solutes in a re-concentrated solution, and thermally recirculating the sweep gas for reuse.
  • the various embodiments provide a system for recovering draw solution solutes comprising an osmotically driven membrane process (ODMP) system, wherein the ODMP system comprises a feed solution inlet, a draw solution inlet, and a first thermal separation apparatus fluidly connected to the ODMP system, the first thermal separation apparatus comprising: a draw solution stream inlet, a draw solution stream outlet and a first heat and mass transfer device, operated at an elevated temperature, in which volatile solutes are removed from a draw solution by a sweep gas.
  • the system also comprises a second thermal separation apparatus comprising a second heat and mass transfer device, operated at a lower temperature, in which solutes, introduced by the sweep gas, are redissolved to form a reconcentrated draw solution. Recirculation of the sweep gas within the system is caused by use of heat.
  • ODMP osmotically driven membrane process
  • the various embodiments provide a system for recycling draw solutes in an osmotically driven membrane process comprising a means for heating a draw solution comprising dissolved draw solutes and a solvent to increase one or more vapor pressures of the draw solutes, a means for stripping the volatile solutes from the solvent by exposing the draw solution to a sweep gas, a means for cooling the sweep gas and stripped volatile solutes such that the volatile solutes become dissolved solutes in a re-concentrated solution; and a means for thermally recirculating the sweep gas for reuse.
  • the various embodiments also provide a method of recycling draw solutes in an osmotically driven membrane process comprising stripping volatile solutes from the solvent by exposing a draw solution to a sweep gas, and recirculating the sweep gas using thermal pressurization.
  • FIG. 1 is a schematic diagram of an integrated system to recover and reuse heat input in the thermal recovery of a draw solution solute from output streams of an osmotically driven membrane process, according to an embodiment.
  • FIG. 2 is a schematic diagram of an integrated system to recover and reuse heat input in the thermal recovery of a draw solution solute from output streams of an osmotically driven membrane process, according to another embodiment.
  • FIG. 3 is a schematic diagram of an integrated system to recover and reuse heat input in the thermal recovery of a draw solution solute from output streams of an osmotically driven membrane process, according to an embodiment.
  • FIG. 4 is a schematic diagram of a system for thermal recovery of draw solutes according to an embodiment.
  • FIGs. 5A-5C are schematic diagrams of a system for thermal recovery of draw solutes according to another embodiment.
  • FIGs. 6A-6D are schematic diagrams of a system for thermal recovery of draw solutes according to another embodiment.
  • FIG. 7 is a schematic diagram of a system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 8 is a schematic diagram of a system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 9 is a schematic diagram of a system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 10 is a schematic of a diagram system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 11 is a schematic of a diagram system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 12 is a schematic of a diagram system for thermal recovery of draw solutes according to an embodiment.
  • FIG. 13 is a schematic of a diagram system for thermal recovery of draw solutes according to an embodiment.
  • FIGs. 14A-14D are schematic diagrams illustrating the operation of a Stirling cycle thermal pressurizer.
  • FIG. 15 is a schematic diagram of a system for thermal recovery of draw solutes according to an embodiment.
  • ODMP osmotically driven membrane process
  • ODMP system ODMP system
  • conduit refers generally to flow pipes and other fluid flow ducts or conduits known to those of ordinary skill in the art for allowing transport of fluid (e.g., vapor and/or liquid) streams to and/or from system components.
  • fluid e.g., vapor and/or liquid
  • Embodiment systems integrate thermal stripping of draw solution solutes from the dilute draw solution and from a feed stream.
  • the stripping of draw solution solutes from both the draw and feed streams may involve integrating the operation of draw solute recovery mechanisms, one for each stream, that each involves a thermal separation process for either the draw solution or feed stream.
  • Draw solute recovery mechanisms in the various embodiments involve integrated operation of two draw solute stripping operations corresponding to the feed and draw solution streams.
  • the two draw solute stripping operations may be implemented by any of a variety of thermal separation mechanisms, including, but not limited to, distillation columns, membrane distillation arrays, pervaporation arrays, etc.
  • the various embodiments may be used to recover draw solute in any of a number of osmotically driven membrane processes (ODMPs).
  • ODMPs may include forward osmosis (FO) and/or pressure enhanced osmosis (PEO) desalination or water treatment, pressure retarded osmosis (PRO) power generation, and direct osmotic concentration (DOC) of desired feed stream constituent.
  • a first solution (known as a process or feed solution) may be seawater, brackish water, wastewater, contaminated water, a process stream, or other aqueous solution may be exposed to a first surface of the membrane.
  • a second solution (known as a draw solution) with an increased concentration of solute(s) relative to that of the first solution may be exposed to a second opposite surface of the membrane.
  • ammonium ions may move from the second side of the osmosis membrane to the first side of the membrane. Further, sodium ions (Na + ) may move from the first side of the membrane to the second side.
  • Solvent such as water, may be drawn by water flux from the first solution through the membrane, thereby concentrating the first stream and diluting the second stream.
  • the diluted second stream may be collected at a first outlet and undergo a further separation process.
  • purified water may be produced as a product from the solvent-enriched solution.
  • the concentrated first stream may be collected at a second outlet for discharge or further treatment.
  • Such concentrated process solution may contain one or more target compounds which it may be desirable to concentrate or otherwise isolate for downstream use.
  • the draw solutes may be recovered for reuse.
  • the diluted draw solution stream and concentrated feed stream may be directed to draw solute recovery mechanisms involving separate thermal separation apparatuses (e.g., distillation columns, membranes, pervaporation arrays, etc.).
  • low temperature heat may cause the draw solutes in a thermal separation apparatus to evaporate, leaving a product water substantially without said solutes.
  • a heat exchanger may be used to condense a portion of the vapors. In at least one embodiment, about 70% of the vapors may be condensed.
  • An absorber system may be used to introduce a portion of the remaining vapors to absorb into a dilute draw solution stream.
  • a second absorber system may use a concentrated ammonia solution to absorb the remaining draw solute vapors.
  • Liquid streams exiting the condenser, and the first and second absorbers, may be mixed and used as all or part of the concentrated draw solution.
  • Heat may be recovered in the various embodiments using, for example, mechanical vapor compression acting on the vapor streams that are produced by draw solute recovery methods.
  • the heat recovery may involve closed or semi-open heat pumps using heat transfer fluids commonly employed in heat recovery and refrigeration.
  • additional thermal energy may be integrated into the thermal stripping of draw solutes from, by way of example, heat recovered from engines used to generate power and/or drive the heat pump apparatuses; heat rejected from other activities close enough to the ODMP operations as to be accessible for such use.
  • the integrated heat recovery methods transfer latent and/or sensible heat from vapor streams produced during the thermal recovery of volatile draw solution solutes to the thermal recovery operation, such that the draw solution solutes may be reused for the continued recovery of solutes.
  • the integrated heat recovery method may involve increasing condensation temperature of the vapor streams such when they are condensed, the amount of heat transferred to a stream with draw solution solute is sufficient to cause vaporization of the solute.
  • FIG. 1 illustrates an embodiment system for recovering draw solution solutes from product streams and recovering/recycling the heat produced in such solute recovery.
  • System 100 may include an ODMP system, which may be any type of semi-permeable membrane in which water flux is driven from a feed stream to the draw solution stream due to osmotic pressure difference across the membrane (e.g., FO, PRO, PEO, DOC).
  • FO feed stream
  • PRO PRO
  • PEO osmotic pressure difference across the membrane
  • DOC osmotic pressure difference across the membrane
  • the water flux similarly flows from the feed stream, also leaving a concentrated product solute stream, which may be recovered as a target compound.
  • a PRO membrane system like the FO and DOC membrane systems, the water flux from the feed stream leaves a concentrated product solute stream.
  • the initial feed stream may be further substantially unpressurized and diluted.
  • stream 1 is concentrated, and stream 2 (the draw solution) is diluted, by water flux through the membrane system.
  • stream 2 will additionally be pressurized, and subsequently directed to pressure exchangers. While solutes from each stream are substantially rejected from passing the semi-permeable membrane, some amount of solutes from the feed stream may enter the draw solution stream, and solutes from the draw solution stream may enter the feed solution, to varying degrees, depending on the operating conditions of the system. Further, ions from each stream may also cross the membrane, without equal
  • the feed solution may be any solution containing solvent and one or more solutes for which separation, purification or other treatment is desired.
  • Example applications for such treatment may include recovery of purified water recovery for downstream use, removal of undesirable solutes from water, concentration and recovery of desired solutes, etc.
  • the feed solution may be filtered and pre-treated in accordance with known techniques in order to remove solid and chemical wastes, biological contaminants, and otherwise prevent membrane fouling, prior to osmotic separation.
  • the feed solution may be a process stream containing one or more solutes, such as target species, which may be desirable to concentrate, isolate, or recover.
  • target species may include pharmaceuticals, salts, enzymes, proteins, catalysts, microorganisms, organic compounds, inorganic compounds, chemical precursors, chemical products, colloids, food products, or contaminants.
  • the feed solution may be delivered to a forward osmosis membrane treatment system from a source module providing previously- stored feed solution, from an upstream unit operation such as an industrial facility, or from any of a number of other sources, including a salt water body, such as a sea or an ocean.
  • Feed solutions may include various salts and other ionic species such as chloride, sulfate, bromide, silicate, iodide, phosphate, sodium, magnesium, calcium, potassium, nitrate, arsenic, lithium, boron, strontium, molybdenum, manganese, aluminum, cadmium, chromium, cobalt, copper, iron, lead, nickel, selenium, silver, and zinc.
  • Example feed solutions that may be used in the various embodiments include, but are not limited to, aqueous solutions such as seawater, brine and other saline solutions, brackish water, mineralized water, industrial waste water, and product streams associated with high purity applications, such as those affiliated with the food and pharmaceutical industries.
  • aqueous solutions such as seawater, brine and other saline solutions
  • brackish water such as brackish water
  • mineralized water such as those affiliated with the food and pharmaceutical industries.
  • the draw solution in the various embodiments may be an aqueous solution containing a higher concentration of solute relative to the feed solution.
  • the draw solution may generally be capable of generating osmotic pressure within an osmotically driven membrane system.
  • the osmotic pressure may be used for a variety of purposes, including desalination, water treatment, solute concentration, power generation, and other applications.
  • a wide variety of draw solutions may be used. In some
  • the draw solution may include one or more removable solutes.
  • thermally removable (thermolytic) solutes may be used.
  • the draw solution may comprise a thermolytic salt solution.
  • an ammonia and carbon dioxide draw solution may be used, which may be concentrated.
  • Other solutes that may be used in the draw solution include products of ammonia and carbon dioxide gases, such as ammonium carbonate, ammonium bicarbonate, and ammonium carbamate.
  • System 100 may implement draw solute recovery mechanisms in Column A 104 and Column B 106, which may be two of the same or different type of a number of types of thermal separation apparatuses.
  • Example solute recovery systems of Column A 104 and Column B 106 may include distillation columns, distillation membranes, pervaporation membranes, and/or other systems that may cause draw solution solutes, such as ammonia and carbon dioxide solutes to be removed by adding heat to the draw solute recovery system and/or adding pressure to the vapors produced in the draw solute recovery system.
  • distillation columns e.g., fractionating columns
  • pervaporation materials may include natural or synthetic polymers such as polyurethane or natural rubber, or suspended liquid membranes that act as passive or active selective membranes for ammonia and carbon dioxide relative to water vapor.
  • a pervaporation or similar membrane separation method may be used in place of or in conjunction with a distillation column.
  • an absorber column may also be implemented as part of the draw solute recovery system in Columns A and B.
  • System 100 may also include heat exchangers 110, 118, such as reboiler heat exchangers.
  • the heat exchangers may include heating and cooling devices that can be electrical heaters, refrigeration units, solar collectors, and heat exchangers such as steam condensers (described below), circulators and so forth, such as are well known in the art.
  • the heating and cooling devices along with any other equipment used within the process that may have power requirements, can derive their energy from any variety of commonly used sources, including, for example, waste steam, solar energy, wind or geothermal energy, and conventional sources.
  • the system 100 may also include one or more compression devices, such as mechanical vapor compression devices 108, 116 acting directly on the vapor stream(s) of the draw solute recovery methods.
  • the compression devices may be closed or semi-open heat pumps using heat transfer fluids commonly employed in heat recovery and refrigeration.
  • Other combinations of thermal and/or mechanical heat pumps may be employed in conjunction with multiple distillation column staging, either conventional or membrane based, so as to best balance the desire to increase the number of stages while
  • thermocompressor on one or more columns
  • mechanical compressor on one or more other columns
  • heat pump types on other columns, as needed, as well as integration between heat streams as might benefit an absorption heat pump implementation where heat absorbed at a low temperature may deliver a smaller quantity of heat at a higher temperature.
  • Compressors 108, 116 in the various embodiments may be used in some embodiments such that the remaining vapor stream may be compressed to raise its pressure and thereby increase the absorption kinetics.
  • the recycling system may further include a compression operation downstream of the absorber to enhance condensation of draw solute gases.
  • Example components that may be used to perform compression operations include, without limitation, gas compressors, steam eductors, liquid stream eductor, etc.
  • compressor 108 may be omitted.
  • a steam jet may be used in which a small portion of steam may be mixed with vapors to increase pressure to an intermediate pressure between the two streams.
  • an absorbing solution may be pressurized and introduced into an eductor jet to entrain and compress the solute vapor.
  • an absorber with series flow of vapors and series or parallel flow of absorbent may be used in various configurations, using membrane contactors, packing within a column, or similar equipment.
  • series flow of vapor may be coupled with parallel flow of absorbent that has been cooled, such that no cooling need take place within the absorbing device.
  • cooling may take place in the device.
  • a heat exchange area as well as a mass interface area may both be in a single device.
  • mixers may be included in embodiments of the systems to mix various fluid (e.g., vapor and/or liquid) streams.
  • Mixers may be, for example, static mixers, high shear mixers, dispersion mixers, vacuum mixers, etc.
  • mixers may be devices that operate by the Venturi effect (e.g., eductors, thermocompressors, etc.) and are capable of mixing constituent streams that have different pressures.
  • any materials may be used to construct the various holding and/or storage devices (chambers, vessels, and receptacles), conduits, piping, and related equipment, as long as they will withstand the weight of the solutions, and be nonreactive with any solutes within the solutions.
  • Typical materials are non-corrosive, non-reactive materials such as stainless steel, plastic, polyvinyl chloride (PVC), fiberglass, and so forth.
  • the vessels can take any suitable configuration, but are typically cylindrical tanks, contoured or fitted tanks, and so forth.
  • the receptacles are typically water towers, cylindrical tanks, contoured or fitted tanks, and so forth.
  • chambers are shown as separate units, but the invention is not limited to that configuration, and where appropriate, any number of chambers can be contained within a single vessel, for example, partitioned into two chambers separated by the semi-permeable membrane 102.
  • Operation of system 100 may involve various steps to optimize heat recovery and reuse from the recovery of draw solutes.
  • Osmotic pressure difference across the membrane 102 may cause water to flow from the feed solution in conduit 1 on the first side of the membrane to the draw solution in conduit 2 on the second side of the membrane.
  • the ODMP system may produce a concentrated feed stream in conduit lb on the first output side of the membrane and a diluted draw solution in conduit 2b on the second output side of the membrane.
  • the diluted draw solution in conduit 2b may be pressurized and directed to subsequent pressure exchangers (not shown).
  • the diluted draw solution in conduit 2b may be direct to a first thermal separation apparatus (e.g., Column A) 104, which may recover draw solutes for reuse the system 100.
  • the concentrated feed stream in conduit lb may be directed to a second thermal separation apparatus (e.g., Column B) 106, which may recover any reverse salt flux of draw solute that passed from the initial draw solution stream in conduit 2a to the initial feed solution stream in conduit la.
  • Columns A and B may use any one or more thermal separation techniques.
  • draw solution solutes in the dilute draw solution stream may be vaporized, thereby separating the draw solution solutes in outlet conduit 3 from a remaining water stream in outlet conduit 4 that is substantially free from draw solution solutes.
  • any draw solute in concentrated feed stream in inlet conduit lb may also be recovered by vaporization, thereby producing draw solute vapor and water vapor in outlet conduit 5 and a water stream in outlet conduit 6 that is
  • Column A operates at a higher pressure than Column B.
  • the pressures may be same or reversed, as suits the
  • the vapors in conduit 3 may be directed to an optional compressor 108, which may increase the vapor pressure and thereby raise their condensing temperature.
  • the vapors in conduit 3 and the water stream in conduit 6 may be directed to the heat exchanger 110.
  • heat may be transferred from the vapors provided via conduit 3 to water provided via conduit 6 in the form of latent heat of vaporization released from the condensation of at least a portion of the vapors from conduit 3.
  • Such heat may be applied to vaporize at least a portion of the water stream from conduit 6, which may in turn be reused in the thermal separation process in Column B.
  • conduit 6 recycles the heated water (e.g., water vapor) from heat exchanger 110 back into the inlet of Column B 106.
  • the remaining liquid in the stream in conduit 6 may be collected, such as in a vessel 111, and may be reused with or without modification in the ODMP system.
  • the stream in conduit 6 may be used as the brine waste stream of a FO process, concentrated product of a DOC process, or recombined with the feed solution stream in conduit la.
  • a portion of the heat used in Column A 104 may be recycled for use in Column B 106.
  • the vapor outlet stream from Column A is used to heat a water outlet stream from Column B .
  • the at least partially condensed vapors from conduit 3 may be directed from heat exchanger 110 to a vapor liquid separator (VLS) 112, which may produce vapor in output conduit 7 and liquid in output conduit 8.
  • VLS vapor liquid separator
  • the vaporized draw solution solutes and water vapor in conduit 5 may be combined with the vapor in conduit 7 from the VLS 112 to produce a combined vapor stream in conduit 9.
  • This stream combination may be performed using a mixer 114, which may be any of various types of mixers known in the art.
  • the combined vapor stream in conduit 9 may be compressed in a compressor 116, thereby raising the condensation pressure of the combined vapor stream in conduit 9.
  • the combined vapor stream in conduit 9 may be directed from the compressor 116 to the heat exchanger 118.
  • the heat exchanger 118 may cause condensation of at least part of the combined vapor stream from conduit 9, from which latent and/or sensible heat may be transferred to vaporize at least a portion of the water stream from conduit 4 produced from the thermal draw solute recovery process in Column A 104.
  • the resulting at least partially vaporized stream in conduit 4 may be reused in the thermal recovery process in Column A 104, thereby recycling of heat used in Column A and B to Column A.
  • the vapor outlet streams from Columns A and B may be used to heat the water outlet stream from Column A.
  • the water outlet of heat exchanger 118 may be recycled into the inlet of Column A.
  • the remaining liquid stream in conduit 4 may be collected in a vessel 119 and may be used in the ODMP system.
  • the collected liquid in vessel 119 may be used as the product water of an FO process, the removed solvent of a DOC process, or the working fluid of a PRO process.
  • the at least partially condensed combined stream in conduit 9 may be combined with the liquid stream in outlet conduit 8 from the VLS 112 to form a concentrated draw solution in conduit 10. Such combination may be produced by mixer 120.
  • the solution in conduit 10 may be recycled, with or without modification, to create the initial draw solution in conduit 2a which is provided to the membrane 102. Such recycling of the concentrated draw solution in conduit 10 may be controlled through a valve 122.
  • Embodiments of the heat recovery system 100 may provide several advantages over other systems and methods.
  • One advantage may be that, since vapor in Column A 104 may be subjected to a higher pressure than that of Column B 106, a larger quantity of heat may be required for the separation process in Column A 104 compared to the heat required in Column B 106.
  • the first transfer of heat for reuse to Column B 106 may be down a pressure gradient, and thus more efficient. That is, the less vapor from the higher pressure Column A 104 that is required to condense to transfer the latent heat to Column B 106, the less work may be required in Compressor A 104.
  • composition of the solutes in the feed solution may be such that they are less soluble at higher temperatures, thereby making the lower pressure and temperatures of Column B 106 relative to Column A 104 effective in reducing precipitation in conduit lb or Column B 106.
  • Another advantage may be that due to the lower concentration of draw solution solutes in the vapor separated in Column B 106, the vapor stream in conduit 5 may have a higher condensing temperature that of the compressed vapor in conduit 3 and that of the vapor in conduit 7 produced from operation of the VLS 112. Therefore, the vapor stream 9 resulting from mixing the vapor stream in conduit 5 with the vapor stream in conduit 7 may require a lower degree of compression to achieve latent heat transfer to Column A 104, thereby requiring less work by compressor 116.
  • the heat exchanger 110 may serve as an intercooler, reducing sensible heat of the at least partially vaporized stream in conduit 3 that may result due to compression by compressor 108. Due to the reduced heat, the volume of the vapor stream 7 exiting the VLS 112, and in turn the volume of the combined vapor stream 9, may be reduced, thereby reducing the amount of work required to be performed by compressor 116.
  • compressor 108 in addition to compressor 116, another advantage may be a reduction in the cost of each compressor 108, 116, since the required compression ratio and temperatures of operation of each compressor 108, 116 may be minimized by splitting the total compression work.
  • system 100 may be configured to include only one compressor 116, omitting optional compressor 108.
  • the work required for heat reuse in Column A 104 may be provided solely by compressor 116.
  • FIG. 2 illustrates another example heat recovery system 200.
  • System 200 may be substantially the same as that of system 100, but may adjust the composition of the combined vapor stream in conduit 9 by providing a bypass of all or a portion of the vapor in conduit 7.
  • system 200 may include a flow divider, or other connection capable of splitting one stream into two flow paths, to direct the vapor in conduit 7 to a cooling apparatus, such as a condenser 202.
  • the vapor in conduit 7 may be fully condensed into a condensate stream in conduit 20, thereby reducing the volume and draw solute concentration of the combined vapor stream in conduit 9.
  • the condensed vapor in conduit 20 may be combined with the liquid stream in conduit 8 from the VLS 112.
  • the condensed streams in conduits 20 and 8 may be mixed in mixer 204, which may be any of the various types of mixers known in the art.
  • Embodiments of system 200 may provide several advantages over other systems and methods.
  • One advantage may be a reduction in the amount of work to be performed by compressor 116 due to the reduced volume of the combined vapor stream in conduit 9.
  • Another advantage may be that, since the lower concentration of draw solutes correlates with a higher condensing temperature than the vapor streams in conduit 3 and/or the vapor output in conduit 7 from the VLS 112. In this manner, mixing the vapor in conduit 7 with the vaporized volute stream in conduit 5, such as using a mixer 114, may result in a lower degree of compression required to achieve latent heat transfer to Column A 104.
  • system 200 may include an optional compressor 108.
  • optional compressor 108 may be omitted as unnecessary based on factors including the relative pressures of Column A 104 and Column B 106, the concentrations of the feed stream in conduit lb and draw solution in conduit 2b, etc.
  • FIG. 3 illustrates another example heat recovery system 300.
  • System 300 may be substantially similar to systems 100 and 200, but may change the interaction between the vaporized solutes in conduit 5, recovered in the separation process in Column B 106, and the additional vapor stream in conduit 7, produced by the VLS 112.
  • the vaporized solute stream in conduit 5 may be kept separate from the vapor stream in conduit 7. In contrast to the
  • the heat exchanger 110 may provide heat for Column B which may be directed for reuse in Column A 104
  • the heat exchanger 110 transferring heat into Column B 106 may act only as an interchange cooler for vapor streams directed to heat reuse in Column A 104 (e.g., heat exchanger 118).
  • the vaporized solute stream in conduit 5 may be optionally directed to the optional condenser 202 (shown in FIG. 2) to be condensed, and may then be directed to a mixer 320 to be mixed with the liquid stream in conduit 8 produced by the VLS 112.
  • the liquid stream in conduit 8 may have also been combined with the at least partially condensed stream in conduit 9 generated from operation of the heat exchanger 118.
  • the vapor outlet stream from Column B is not used to heat the water outlet stream in the embodiment system 300.
  • Embodiments of system 300 may provide several advantages over other systems and methods.
  • One advantage may be that the heat exchanger 110, acting as an intercooler, may reduce the sensible heat from compression in compressor 108, and thereby reduce the temperature and volume of the vapor stream in conduit 7 produced by the VLS 112. Due to the reduction in volume, the amount of work needed to be performed by compressor 116 may be reduced.
  • one advantage from using compressor 108 in addition to compressor 116 may be reduction in cost of each compressor 108, 116, since the required compression ratio and temperatures of operation of each compressor 108, 116 may be lowered as a result of splitting the total compression work.
  • compressor stages may be applied to the vapor streams of the draw solute recovery processes in Column A 104 and/or Column B 106.
  • a sweep gas such as nitrogen, air, helium and/or argon is used in a falling film heat exchanger for the recovery of volatile solutes within an osmotically driven membrane process.
  • the system 100 may be configured to use heat to compress the sweep gas to induce flow through the system 100.
  • Draw solutes that are thermally separable from solution by heating to form a gaseous phase of the solute require a way of removing (which may be referred to as "stripping") them from the solution, to allow their continuous reuse.
  • a way of removing which may be referred to as "stripping"
  • One example of such an application is the stripping of ammonia and carbon dioxide from a solution of ammonium salts, as discussed above.
  • Steam stripping may be performed across a range of pressures, typically involving heating product water in a reboiler or similar device, such as Column A above, and using the steam thus produced to strip the draw solutes from solution. These solutes are then condensed and reused.
  • the following embodiments provide a less energy-intensive separation way for separating volatile solutes from solution.
  • the following embodiments use heat to induce a change in phase predominantly of the solutes, rather than the solvent in a way that minimizes the creation or use of steam.
  • One way of achieving this is to introduce sufficient heat to the draw solution to cause the vapor pressure of the draw solutes to increase to within a desired range, and then use a sweep gas, such as, by way of non-limiting example, air or nitrogen, to strip the solutes from solution, thereby minimizing the removal of water vapor in the process. If the sweep gas already contains humidity, or is caused to do so, the removal of water vapor will be
  • the mixture of sweep gas and gaseous solutes may then be cooled in the presence of solvent, including by way of non-limiting example, diluted draw solution, causing the solutes to be reintroduced into solution and allowing for reuse in a more concentrated draw solution.
  • solvent including by way of non-limiting example, diluted draw solution, causing the solutes to be reintroduced into solution and allowing for reuse in a more concentrated draw solution.
  • the sweep gas may then be cooled and substantially reduced in concentration of draw solutes and may be recycled and reused for continued draw solute stripping.
  • thermolytic salts such as ammonium salts
  • the temperature of the draw solution is maintained at or above the temperature at which the solutes become separable through stripping, and high enough for the desired rate of solute removal.
  • the temperature of the draw solution is lowered. Continuous or periodic introduction of heat to the solution may be performed to continue the stripping process.
  • heat exchangers 110, 118 may be placed in-between stripping stages, to raise the temperature of the solutions such that by the time the solutions exit the stripping stage the temperature is still sufficient for solute stripping. In such a configuration, however, a significant portion of the stripping occurs at a temperature that may be higher than that which is minimally required. At higher temperatures, the vapor pressure of water also rises and therefore more water will also be stripped as humidity in the sweep gas stream. This results in the use of more thermal energy than would be used if the draw solution were kept at a constant, lower temperature. This represents inefficiency in the stripping process and introduces complexity to the piping, number of heat exchangers and mass contact devices, and overall process management.
  • the sweep gas is brought into contact with the draw solute-containing solutions with the use of a falling film heat exchange device.
  • the draw solution, brine stream or other process stream containing draw solutes is provided as a descending film on the surface of a heat exchange material.
  • the sweep gas is flowed over this film, stripping the volatile solutes.
  • Heat may be continuously introduced through the heat exchange material, maintaining a largely constant temperature of the draw solution, minimizing the vaporization of water along with draw solutes, allowing for the use of lower temperature heat sources and simplifying the overall process equipment and its operation.
  • the falling film heat exchange device may comprise polymeric heat exchange hollow fibers.
  • a polymeric hollow fiber heat exchanger may offer a much higher surface area for heat exchange and film formation than that possible with metallic heat exchangers, at an equivalent or lower cost.
  • a 1.3 mm inner diameter fiber may allow the packing of over 90 m of surface area in a heat exchanger occupying a cylinder 8 inches in diameter and one meter long.
  • a metal heat exchanger with 0.5 inch inner diameter tubes would provide only 13 m in the same volume, a nearly 7-fold difference.
  • Polymeric heat exchangers offer the further benefit of being free of the corrosion to which metal heat exchangers are susceptible, particularly with respect to the use of heated, saline solutions.
  • a falling film heat exchanger may be used as a condenser for the re-absorption of draw solutes.
  • a largely solute free water or dilute draw solution would flow on one side of a heat exchange surface, on the other side of which would be a cooling fluid.
  • the sweep gas would pass over the cooled, dilute draw solution and absorption of the draw solutes would cause a net flow of draw solutes from the sweep gas into the draw solution, thereby concentrating it and leaving the sweep gas largely free of solute.
  • the heat exchange materials may be, by way of non-limiting example, tubes, plates, spirals, or hollow fibers.
  • the liquid may flow on the inner or outer surface of the tube or hollow fiber, with the heating or cooling source on the opposite side.
  • the sweep gas will be on the same side of the heat exchange surface as the solution having solutes removed by, or introduced from, the sweep gas stream.
  • Flow of gas and liquid may be in co-current or counter-current flow. Cooling or heating fluids may be provided in either co-current, counter-current flow or in a phase change configuration in which steam is introduced orthogonally to the heat exchange surface. Other flow configurations as may be practiced in heat exchange may also be used based on the desired heat transfer performance.
  • a flow of compressed gas may be generated by heat alone, without the introduction of mechanical work, or with minimal mechanical work to facilitate the primarily thermally driven process, by heating gas in a closed vessel or vessels until the gas has reached the desired pressure. This may be followed by alternating the heating and cooling of one or more vessels in such a way that a steady stream of compressed gas is caused to be accumulated and or flow.
  • a method may be used to induce a flow of sweep gas in a system designed to remove and recycle volatile solutes from the draw solution, brine stream, or other process stream, of an osmotically driven membrane process, such that the primary energy input to such a process is thermal.
  • an intermediate process or device may be used to convert thermal energy into a compressed gas stream, which may be used for sweep gas removal of draw solutes in an as osmotically driven process.
  • Such an intermediate process may involve the use of a working fluid, such as in the Stirling cycle.
  • a Stirling engine could be used to convert waste heat from a geothermal or power plant reject source into a motive force for the circulation of a sweep gas stream, or an open Stirling cycle could be employed, using the sweep gas as its working fluid.
  • An example of the modification of a Stirling cycle for gas compression is illustrated in Figures 14A-14D and described in more detail below.
  • FIG. 4 An embodiment of a sweep gas recovery system is shown in Figure 4.
  • a diluted draw solution of ammonium salts 1 is directed to a hollow fiber polymeric heat exchanger (HX) 2 and caused to flow by gravity in a film on the interior surface of the hollow fibers by use of a distributor (not shown) in the heat exchanger 2.
  • a flow of nitrogen sweep gas 3 is flowed in a counter-current configuration relative to the diluted draw solution 1.
  • Heat is introduced to the shell side of the heat exchanger 2 with low-pressure steam 6 of approximately 40-60 °C, such as 50 °C, which condenses on transferring its heat to the liquid film through the polymeric heat exchange fiber.
  • the film is then maintained at a temperature of approximately 42-48 °C, such as 45 °C, causing a portion of the draw solutes to be in gaseous form.
  • the condensed steam 7 is returned to the heat source for reuse.
  • the sweep gas 3 picks up gaseous draw solutes, such as ammonia and carbon dioxide, and removes these gases from the diluted draw solution 1, resulting in a substantially solute free product water 4, such as a desalinated water product of the FO process.
  • the sweep gas enriched in draw solute gases 5 is then directed to the shell side of a second polymeric hollow fiber heat exchanger 40.
  • a stream of diluted draw solution is provided via a conduit 8 and a distributor (not shown) to flow on the outer surface of the heat exchange fibers.
  • Cooling water 11 is provided to the lumen of the heat exchange fibers, picking up heat and exiting 12 to be returned to the cooling source.
  • Cooling of the enriched sweep gas 5 in the presence of the cooled dilute draw solution causes the ammonia and carbon dioxide gases to absorb into the solution, forming draw solutes and concentrating the draw solution for reuse in the FO process via conduit 10.
  • the sweep gas 1, now substantially free of draw solute gases 9 may be directed to a thermal pressurizer 13 which uses heat to compress the sweep gas 1 for reuse via conduit 3, without the need for electrical or shaft work, thereby allowing the process to run continuously and operating primarily with low temperature heat.
  • diluted draw solution 1 may be directed to the shell side or lumen side as desired in either or both of the hot heat exchanger 2 and cold heat exchanger 40.
  • Hot water, glycol, oil, or other fluids may be used to provide heat instead of steam.
  • a phase change refrigerant, salt solution, or other fluid may be used as a cooling stream.
  • Multiple heat exchangers may be used in parallel or serial configurations in either hot or cold heat exchange operations to achieve desired system performance.
  • the heat exchangers may be operated in horizontal or diagonal configurations, causing the film to flow in a variety of manners along the heat exchange surface.
  • metal heat exchangers may be used, in shell and tube, plate and frame, spiral, or other configurations.
  • the sweep gas may be composed of air, nitrogen, argon, helium, or various other gases.
  • the diameter of the heat exchange tubes or fibers may be between approximately 1-25 mm, such as between 5 -10 mm.
  • Product water may be provided via conduit 8 rather than dilute draw solution, or these may be mixed as desired to control the rate of absorption and final
  • Stream 1 may alternately be volatile draw solute containing solutions other than a dilute draw solution, such as, by way of non-limiting example, FO membrane system brine.
  • a closed cycle Stirling engine 13 may be used for the recycling of the sweep gas 3.
  • a conventional compressor powered by solar energy or other energy may be used when appropriate for the energy sources available.
  • FIGS 5A-5C illustrate an embodiment of a Stirling cycle analogous pressurizer 13.
  • a thermal pressurizer 13 is formed from two heat exchangers HX and two pipe sections. Heat is introduced to one heat exchanger HX and removed from the other.
  • a displacement piston 42 is used to move fluid, such as water, to cause one or the other heat exchange surfaces to be covered in fluid, and thereby not in contact with the gas to be compressed within the Stirling cycle air compressor 13.
  • Two valves 122 A, 122B are placed on the non-fluid filled pipe, one for gas inlet (e.g. 122A), and one for outlet (e.g. 122B).
  • Regenerator packing 46 such as stainless steel mesh, is placed in the non-fluid filled pipe to act as the regenerator in the Stirling cycle.
  • stage 1 The operation of the Stirling compressor 13 occurs in four stages.
  • stage 1 the displacement piston 42 is positioned so that the hot heat exchanger HX surface is largely covered in liquid. Preferably, this liquid has a low heat capacity and low volatility.
  • the remainder of the compressor 13 is filled with sweep gas.
  • stage 1 the cooling heat exchanger HX cools the sweep gas. This causes the gas pressure to drop.
  • the inlet valve 122 A is opened, allowing additional sweep gas to enter the compressor 13.
  • the inlet valve 122A is closed and the
  • displacement piston 42 is moved to a position that causes the hot heat exchanger HX surface to be exposed and the cold heat exchanger HX surface to be covered by the liquid. This causes the sweep gas to be heated, increasing its pressure.
  • the outlet valve 122B is opened, releasing the pressurized sweep gas.
  • the outlet valve 122B is closed, and the displacement piston 42 is moved to a position that covers the hot heat exchanger HX surface and exposes the cooling heat exchanger HX surface, which then returns the device to stage 1.
  • These stages are repeated, allowing for continuous gas pressurization.
  • the regenerator 46 reduces the movement of heat between the two heat exchangers HXs.
  • a portion of the pressurized sweep gas is used to drive the displacement piston 42, causing the gas compressor 13 to operate entirely on heat as its energy source.
  • the inlet and outlet valves 122A, 122B may be placed in separate (e.g. different) locations.
  • the liquid may be water, oil, glycol, or other liquids as may be suitable to the purpose, or a gas with a density significantly greater than the gas to be compressed.
  • the compressor 13 may be operated without the use of a liquid.
  • the displacement piston 42 may be used vertically.
  • the heat exchangers HXs may be horizontal or at an angle. Further, multiple heat exchangers HXs may be used in parallel to provide a desired heat exchange surface area.
  • the length of the regenerator packing 46 and pipes may vary as needed to obtain a desired performance.
  • Multiple compressors 13 of the type described herein may be used in parallel to optimize capital costs relative to available components.
  • multiple compressors 13 of the type described herein may be used in series as stages to achieve higher compression ratios.
  • Tanks may be used before and/or after the compressor 13 for sweep gas inlet and outlet flows, to smooth the delivery and use of the sweep gas within the solute recycling system.
  • the displacement piston 42 may be insulated to prevent heat transfer between the two liquid bodies in contact with the hot and cold heat exchangers HXs.
  • Gas may be provided on the tube or shell side of each heat exchanger HX as desired.
  • steam is condensed on the shell side of the hot heat exchanger HX and gas is on the tube side.
  • hot oil is on the tube side of the hot heat exchanger HX and gas is on the shell side. Similar permutations may be explored with the cold heat exchanger HX.
  • the compressor 13 does not include a
  • a regenerator packing 46 may be used on the liquid side as well, to reduce heat transfer between the hot heat exchanger HX and cold heat exchanger HX through the displacement liquid.
  • the rotation may be powered, for example, by compressed air, electrical power, or mechanical shaft work.
  • the rotation may be either alternating - clockwise and counter clockwise, for example, or performed continuously in one direction. In either case, the liquid will be at the lowest point of the compressor 13 and is therefore not lifted in elevation. Further, the volume of the compressor 13 will be constant, such that the energy required for the rotation would be minimal. In a rotating compressor 13, the revolutions per minute would set the cycle time of the compressor 13.
  • the compressor 13 may be square, as shown in Figures 5A-5C, rectangular, or circular to reduce resistance to rotation. Rotation may be performed in either direction (e.g. clockwise or counterclockwise).
  • the packing for the regenerator 46 may be chosen so that the resistance to flow of the displacement fluid during rotation is similar to the resistance to the flow of the liquid through the heat exchangers HX in the configuration chosen (shell or tube side flow), so as to smooth rotation. Alternately, no packing may be used.
  • a flywheel may be used to smooth rotation as well.
  • FIG. 6A-6D A preferred rotating compressor embodiment is shown in Figures 6A-6D.
  • the displacing liquid is covering the hot heat exchanger HX 2 on the tube side, preventing the hot heat exchanger HX 2 from contacting the gas.
  • Gas occupies the volume of the shell side of the cold heat exchanger HX 1 and the void spaces of the regenerative packing 46 on two sides 4, 5 of the compressor 13.
  • Hot oil may be flowed on the tube side of the hot heat exchanger HX 2 and cooling water flowed on the tube side of the cold heat exchanger HX 1.
  • the gas is cooled, reducing its pressure, until the desired pressure is reached. Then the gas is allowed to enter the compressor 13 through the inlet valve 3.
  • stage two the compressor 13 is rotated counterclockwise, causing the displacing liquid to occupy the void space of the regenerator packing 46 on side 4 of the compressor 13, delivering heat the liquid received from the hot heat exchanger HX 2 to the regenerator material 46, thereby cooling the liquid. Gas is displaced from the regenerator packing 46 on side 4 to the other regenerator packing 46 on side 5, and continues to occupy the shell side of the cold heat exchanger HX 1.
  • stage three the compressor 13 is again rotated counterclockwise, causing the displacing liquid to cover the heat exchange surface of the cold heat exchanger HX 1 , preventing it from contacting the gas.
  • the gas is displaced to occupy the heat exchange area of the hot heat exchanger HX 2, the unheated regenerator packing 46 on side 5 and the hot regenerator packing 46 on side 4, transferring the heat removed from the displacing liquid during rotation to the gas.
  • heating of the gas causes its pressure to rise, until a desired pressure is reached. At this point, a portion of the pressurized gas is released through the outlet valve 6. During this phase, both regenerators 46 are heated.
  • stage four the compressor 13 is rotated counterclockwise, causing the displacing fluid to occupy the void space of the regenerator 46 on side 5, transferring the heat received by the regenerator 46 during stage 3 to the displacing fluid.
  • the compressor 13 is rotated counterclockwise once more to return it to stage one, allowing for the continued operation of the compressor 13.
  • Figure 7 illustrates a non-limiting embodiment of the use of heat to induce the flow of a sweep gas for the recovery and reuse of a volatile draw solute.
  • the osmotically driven membrane portion of the osmotic process is not shown, but rather only the draw solute recycling is depicted.
  • Compressed sweep gas is accumulated in a tank 1 and released to act as a sweep gas via conduit 2 for stripping of draw solutes from a draw solution in a liquid/gas contacting device 3, such as a packed column.
  • An optional valve located between the tank 1 and liquid/gas contacting device 3 may be provided.
  • a diluted draw solution 12 is directed to the liquid/gas contacting device 3 and becomes product water 15 after its draw solutes are removed.
  • the sweep gas now enriched in volatile draw solutes exits the liquid/gas contacting device 3 via conduit 4 and is cooled in a condenser 5 in the presence of a dilute draw solution 13 to facilitate the re-absorption of the draw solutes into a re-concentrated stream 14, which is returned to the membrane process.
  • the cooled sweep gas 6 undergoes further cooling by the removal of heat 11.
  • the flow of sweep gas into heat exchanger 8 is enabled when the pressure of the gas in the heat exchanger 8 is lower than the pressure of the gas in the condenser 5.
  • the valve 9 for the exit of gas from the heat exchanger 8 is closed, such that gas accumulates in the heat exchanger 8 until its pressure is in equilibrium with the heat exchanger temperature.
  • the inlet valve 7 is closed, while the outlet valve 9 remains closed and heat 10 is introduced to the heat exchanger 8. This causes the pressure of the gas in the heat exchanger 8 to increase.
  • the outlet valve 9 opens, allowing flow of the gas into the tank 1. This flow causes the pressure in the heat exchanger 8 and the tank 1 to equalize, resulting in the outlet valve 9 closing.
  • the heat exchanger 8 is cooled and the inlet valve 7 is opened to continue the cycle. In this manner, a single heat exchanger 8 may be used to cause the thermal pressurization of a sweep gas to provide the motive force for gas circulation in a draw solute removal and recovery system.
  • FIG. 8 The embodiment shown in Figure 8 is similar to that illustrate in Figure 7. However, in this embodiment, two heat exchangers 9, 10 are used in alternate cycles of heating and cooling to provide a more constant and consistent flow of pressurized gas. Any number of heat exchangers 9, 10 may be used in parallel in this manner to improve process performance. [00100] In the embodiment of Figure 9, two heat exchangers 8, 10 are used in series, such that the alternation of heating and cooling of a single heat exchanger 8 may be avoided. In this embodiment, lean sweep gas is allowed to flow through an entrance valve 7 into a heat exchanger 8, which is undergoing constant cooling.
  • a valve 9 between the two heat exchangers 8, 10 periodically opens, as valve 7 closes, allowing a flow of gas from the cold heat exchanger 8 into a continuously heated heat exchanger 10.
  • These two heat exchangers 8, 10 are allowed to equilibrate in pressure, at which point the valve 9 between them closes.
  • the outlet valve 11 for the heated heat exchanger 10 remains closed, resulting in the pressurization of the gas in the heated heat exchanger 10.
  • the gas is released through the valve 11 between the heat exchangers 8, 10 until an equilibration of pressure, at which point the valve 11 is closed.
  • the cool heat exchanger 8 continues to cool the gas within it, and then its entrance valve 7 is re-opened, continuing the cycle.
  • the size of the cooling heat exchanger 8 is ideally larger than the heating heat exchanger 10, and the flow between these may ideally be moderated by the use of a floating piston gas diffuser of the type used in Stirling engines discussed above.
  • a compressor 7 is used to facilitate the flow of gas in conduits 6, 8 into the heat exchanger 10 so as to make the overall system more efficient, in that cooling of the heat exchanger 10 is either reduced or eliminated.
  • the compressor 7 functions in the manner of a diffuser in a Stirling engine, moving the working fluid (in this case the sweep gas) between the condenser 5 and the hot heat exchanger 10.
  • the circulation of sweep gas in conduits 6, 8 is achieved by the use of a heat driven Stirling cycle compressor 7, either in the form of a conventional Stirling engine or open Stirling cycle compressor, in which the sweep gas is the working fluid.
  • FIG 12 illustrates another embodiment of a liquid/gas contacting device 3.
  • membrane contactors 48 are used.
  • the membrane contactors 48 are connected in a "pyramidal" array 50, such that the volume of the gas flow increases from one end to the other.
  • the sweep gas enters the array at the low volume (single contactor 48) end of the array. As the sweep gas strips draw solutes from the draw solution, the sweep gas volume increases.
  • the increase in sweep gas volume is accommodated by the increase in the number of contactors 48 in parallel at each stage of the array (three stages shown), before exiting at the large volume end of the array.
  • the draw solution in this embodiment flows in the opposite direction of the sweep gas flow.
  • FIG. 13 shows a two stage membrane contactor array 50 with a heat exchanger HX between the stages and heat exchangers HX at the draw solution inlet, to ensure that the draw solution maintains a temperature to keep the draw solutes in a volatile state while being stripped.
  • This embodiment also includes a Stirling engine 7 to provide the motive force to overcome frictional resistance to gas flow for the circulation of the sweep gas.
  • Figures 14A-14D illustrate an example of a Stirling cycle analogous gas pressurizer 7 that may be used to induce the flow of stripping gas in the system (from "An oil free air compressor based on the Stirling cycle" by Alexander Peter
  • a pressurizer of this type may be used, by way of non-limiting example, in the manner of Figure 11, operating in the location designated by the number 7.
  • the thermal pressurizer 7 includes a heater 50, a cooler 54 and a regenerator 46 located between the heater 50 and the cooler 54.
  • the thermal pressurizer 7 also includes a chamber 56 with a gas inlet 122 A and a gas outlet 122B and a displacement piston 42 located inside the chamber 56.
  • the portion of the chamber 56 adjacent the heater 50, the hot portion 56h, is at a higher temperature then the portion of the chamber 56 adjacent the cooler 54, the cold portion 56c.
  • the displacement piston 42 is located adjacent the heater 50.
  • a gas such as air in the Glassford device (or sweeper gas in the systems discussed above) is provided into the chamber 56 via the gas inlet 122A into the cold portion 56c of the chamber 56.
  • the gas is provided at a pressure Pi and a temperature T c (cold).
  • T c temperature
  • the displacement piston 42 is moved toward the cooler 54 as illustrated in Figure 14B.
  • Some of the gas in the chamber 56 is displace towards into the hot portion 56h of the chamber 56.
  • the gas increases in temperature.
  • the total volume of the chamber 56 is constant.
  • the pressure inside the chamber 56 increases to a higher pressure P 2 .
  • the displacement piston 42 moved to the cool end of the chamber 56 and is located adjacent the cooler 54.
  • a small amount of gas is located at in the cool portion 56c of the chamber 56 at a pressure P 2 and a temperature T c .
  • the majority of the gas is located in the hot portion 56h of the chamber 56 and is at a pressure P 2 and a temperature T h (hot).
  • the temperature of the gas is raised at a constant pressure P 2 .
  • the displacement piston 42 is then moved back to its original starting position adjacent the heater 50.
  • a majority of the gas is located in the cold portion 56c of the chamber 56 and is at a pressure Pi and a temperature T c .
  • the temperature of the gas is lowered at a constant pressure Pi. The cycle may then be repeated.
  • FIG. 15 illustrates another embodiment of the sweep gas solute recycle system.
  • the aqueous membrane system of the osmotically driven membrane process is not shown.
  • diluted draw solution 1 from an osmotically driven membrane process such as forward osmosis or pressure retarded osmosis, is directed to a heat exchanger 3 to cause its temperature to be raised such that a portion of the draw solutes convert to the vapor phase and the vapor pressure is increased sufficiently for sweep gas stripping from solution.
  • This solution 4 is directed to two or more membrane contactors or other gas/liquid contactors 7, 8, at which point draw solute is stripped from solution by sweep gas 18, 19.
  • the draw solution is further directed to a heat exchanger 11 to keep the temperature high enough for continued stripping of draw solutes, at which point the solution 12 is directed to a second array of one or more contactors 13 for continued stripping of the solutes.
  • This may be done with a pyramidal configuration of contacting devices, with sufficient length of flow channel and area of contact to allow for the desired stripping of draw solutes by the sweep gas 15, which may be nearly complete, producing product water, in the case of FO, or working fluid, in the case of PRO (stream 14).
  • the sweep gas now containing gaseous draw solutes 21, is directed to a cooling heat exchanger / condenser 26.
  • Dilute draw solution 37 may also be directed to the heat exchanger 26 to facilitate the solution of the draw solutes.
  • the fully condensed and solubilized draw solutes exit the heat exchanger 26 as a reconcentrated draw solution 38 for reuse in the aqueous membrane process.
  • the sweep gas, now largely free of draw solutes 33, 34 is directed to the thermal pressurizer sub-system 31, which operates in the manner described in Figures 14A-14D above, with the exception that the condenser of the draw solute recycling system is integrated into the pressurizer system, and the valve 22 on the sweep gas inlet to the cooler may be used instead of or along with the valve for inlet gas on the pressurizer 35 to facilitate the operation of the pressurizer cycle.
  • the pressurized sweep gas 15 exits valve 36, for reuse in the draw solute recycling system.
  • a reservoir tank (not shown) may be used on the gas stream 15 to accumulate pressurized sweep gas to allow for intermittent or otherwise variable operation of the system.
  • the displacement piston 32 is caused to operate by use of an external drive to cause its motion within the chamber 31.
  • This drive may be an air motor, taking a portion of the pressurized gas stream 15, and depressurizing it, sending a small portion of gas to the low pressure inlet line 23, using the change in pressure to drive the piston 32 through its displacement cycle.
  • an electric drive may be used to cause the displacement piston 32 to function. In either case, the work needed to drive the displacement piston 32 is small relative to the transfer of potential energy from heat to pressure.
  • the pressurization of the sweep gas is used overcome the pressure drop of the flowing gas through the gas/liquid contactor device(s) 7, 8, 13 and piping, as well as the force to convey the gaseous solutes with the sweep gas stream. For this reason, the system does not require high pressure pipes, fittings, or vessels.
  • the total heat required for the solute recycling system is: the sensible heat required to heat the draw solution to a temperature at which draw solutes have sufficient vapor pressure (in the case of NH 3 /CO 2 solutes, above approximately 38 C at 1 atm absolute, depending on the ratio of ammonia to carbon dioxide); the enthalpy of solution of the draw solutes; the enthalpy of vaporization of the draw solutes; and the heat required to operate the air compressor cycle.
  • This total quantity of heat is typically lower than that required for steam stripping of the draw solutes.
  • the pressure of the stripping operation may be atmospheric, even at low temperatures of the draw solution. This provides additional advantage over steam stripping, which at low temperatures should be performed under vacuum. Vacuum may be used in the sweep gas system to reduce the gas/liquid contactor area and the temperature of draw solution required, but this is not necessary for low temperature operation.
  • the use of the sweep gas allows for the reduction of the footprint of the system, as a large volume of sweep gas may be used in the thermal pressurization system contemplated herein without requiring a large electrical or fuel energy input.
  • a small membrane contactor system may be used in such a system, rather than a large contactor system or a tall distillation column.
  • an osmotically driven membrane system may be used that has a predominantly low temperature heat as its energy input (excepting low power requirements for fluid pumping in the aqueous membrane system), operates at atmospheric pressure and has a relatively small membrane contactor system rather than a large contactor system or distillation column, as used in a steam stripping apparatus.
  • the heating of the hot side of a thermal pressurizer may be facilitated by injecting a small quantity of heated fluid, for example, hot water, gas, or steam, to add heat to the chamber and induce turbulence for improved gas mixing and heat transfer performance.
  • a small quantity of heated fluid for example, hot water, gas, or steam

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne un procédé et un système pour le recyclage de solutés d'extraction dans un procédé à membrane osmotique. La recirculation du gaz de balayage dans le système est provoquée par l'utilisation de chaleur.
PCT/IB2015/051179 2014-01-27 2015-02-17 Systèmes et procédés de récupération thermique de solutés d'extraction WO2015111033A1 (fr)

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US201461931691P 2014-01-27 2014-01-27
US61/931,691 2014-01-27
US201461950755P 2014-03-10 2014-03-10
US61/950,755 2014-03-10

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WO2018064129A1 (fr) * 2016-09-27 2018-04-05 Oasys Water, Inc. Procédés sur membrane à entraînement osmotique et systèmes et procédés pour la récupération de soluté d'extraction
CN109092005A (zh) * 2018-09-26 2018-12-28 天津明亮工程技术有限公司 一种低沸点溶媒回收方法及回收系统
CN114856766A (zh) * 2022-04-21 2022-08-05 国能龙源环保南京有限公司 联合光伏发电使用的尿素溶液储存运输系统与方法
EP4182047A4 (fr) * 2020-07-15 2024-08-28 Energy Integration Inc Procédés et systèmes pour optimiser la compression de vapeur mécanique et/ou la compression de vapeur thermique dans des processus à étages multiples

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US20040000521A1 (en) * 2002-06-12 2004-01-01 Membrane Technology And Research, Inc. Separation process using pervaporation and dephlegmation
US20120067819A1 (en) * 2009-10-28 2012-03-22 Oasys Water, Inc. Osmotically driven membrane processes and systems and methods for draw solute recovery
US20120267306A1 (en) * 2009-10-30 2012-10-25 Oasys Water, Inc. Osmotic separation systems and methods
US20120273417A1 (en) * 2009-10-28 2012-11-01 Oasys Water, Inc. Forward osmosis separation processes
US8491795B2 (en) * 2011-09-01 2013-07-23 Kenneth Yat-Yi Chen Conversion of seawater to drinking water at room temperature

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040000521A1 (en) * 2002-06-12 2004-01-01 Membrane Technology And Research, Inc. Separation process using pervaporation and dephlegmation
US20120067819A1 (en) * 2009-10-28 2012-03-22 Oasys Water, Inc. Osmotically driven membrane processes and systems and methods for draw solute recovery
US20120273417A1 (en) * 2009-10-28 2012-11-01 Oasys Water, Inc. Forward osmosis separation processes
US20120267306A1 (en) * 2009-10-30 2012-10-25 Oasys Water, Inc. Osmotic separation systems and methods
US8491795B2 (en) * 2011-09-01 2013-07-23 Kenneth Yat-Yi Chen Conversion of seawater to drinking water at room temperature

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018064129A1 (fr) * 2016-09-27 2018-04-05 Oasys Water, Inc. Procédés sur membrane à entraînement osmotique et systèmes et procédés pour la récupération de soluté d'extraction
CN109092005A (zh) * 2018-09-26 2018-12-28 天津明亮工程技术有限公司 一种低沸点溶媒回收方法及回收系统
EP4182047A4 (fr) * 2020-07-15 2024-08-28 Energy Integration Inc Procédés et systèmes pour optimiser la compression de vapeur mécanique et/ou la compression de vapeur thermique dans des processus à étages multiples
CN114856766A (zh) * 2022-04-21 2022-08-05 国能龙源环保南京有限公司 联合光伏发电使用的尿素溶液储存运输系统与方法

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