System and method for separating solvent from fluid

Abstract

To provide systems and methods for removing a solvent, such as water, from a fluid using a redox flow electrochemical separation device.SOLUTION: An electrochemical system has a first reservoir 106 receiving a feed stream 102. The feed stream includes a solvent and a solute different than salt. A second reservoir 108 receives a brine stream 122 with a higher salt concentration higher than the feed stream. Electrodes 116, 118 contact a loop 154 of redox-active electrolyte material causing reversible redox reactions. The reactions cause the loop to accept a first ion from the salt in the first reservoir and drive a second ion into the brine stream in the second reservoir. Three ionic exchange membranes 110, 112, 114 of alternating type define the first and second reservoirs. A concentrate stream 144 is output from the first reservoir, the concentrate stream having a second solute concentration greater than a first solute concentration.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to systems and methods for removing solvents such as water from fluids using a redox flow electrochemical separation device.

Background Art

[0002] In some industries, processes for removing solvents (e.g., water, alcohol) from solutions are utilized. For example, the food and beverage industry may want to remove water to form concentrated and easily shipped foods such as juice concentration, powdered beverage formation, and whey processing. In this example, the concentrated stream is valuable to the producer. Waste treatment plants may also want to extract clean water from waste streams. In this case, the solvent itself is valuable to the processor, and the concentrate has no value.

[0003] Currently, solvent removal can be performed in various ways, such as methods that evaporate the solvent (heating), methods that filter only the solvent under high pressure (reverse osmosis), and methods that extract the solvent across a membrane into an inducing solution with a higher osmotic pressure (forward osmosis). Using thermal energy can sometimes affect the final product (e.g., heating can change the taste of food) and also uses a significant amount of energy. Forward osmosis and reverse osmosis do not necessarily heat the flow but can be more expensive to implement.

Summary of the Invention

[0004] Embodiments described herein relate to electrodialysis apparatus. In one embodiment, the electrochemical system includes a first reservoir containing a supply stream. The supply stream comprises a solvent, a salt having a first salt concentration in the supply stream, and a solute different from the salt at a first solute concentration. A second reservoir contains a brine stream having a second salt concentration higher than the first salt concentration. A first electrode is in contact with a first solution of a first redox-active electrolyte material and is configured to have a first reversible redox reaction with the first redox-active electrolyte material and to receive a first ion from the salt in the first reservoir. A second electrode is in contact with a second solution of a second redox-active electrolyte material and is configured to have a second reversible redox reaction with the second redox-active electrolyte material and to feed a second ion into the brine stream in the second reservoir. An energy source is configured to supply potential to the first and second electrodes. A first membrane having a first ion exchange type is positioned between the first and second reservoirs. A second membrane having a second ion exchange type different from the first ion exchange type is positioned between the first electrode and the first reservoir. A third membrane having a second ion exchange type is positioned between the second electrode and the second reservoir. Flue containing the solvent and a third salt concentration is discharged from the second reservoir. The solvent is removed from the first reservoir via electroosmosis and forward osmosis. A concentrated flow is discharged from the first reservoir. The concentrated flow has a fourth salt concentration that is less than the first, second, and third salt concentrations, and a second solute concentration that is greater than the first solute concentration.

[0005] Other embodiments relate to a method involving introducing a supply flow containing a first salt concentration into a first reservoir defined by a first ion exchange membrane and a second ion exchange membrane of an electrochemical cell. The second ion exchange membrane is a different type of membrane from the first ion exchange membrane. The supply flow contains a solute different from the salt at the first solute concentration. The method further involves introducing a second fluid flow containing a second salt concentration higher than the first salt concentration into a second reservoir of the electrochemical cell. The second reservoir is defined by a first ion exchange membrane and a third ion exchange membrane. The third and second ion exchange membranes are of the same type. An external voltage is applied to the first and second electrodes of the electrochemical cell. A solution containing a redox-activated electrolyte material circulates between the first and second electrodes. The redox-activated electrolyte material is reduced upon contact with the first electrode and oxidized upon contact with the second electrode. In response to the reduction and oxidation of the redox-activated electrolyte material, ions are transported across the first, second, and third ion-exchange membranes to remove the solvent and salt from the first reservoir via electroosmosis and forward osmosis. The effluent is discharged from the second reservoir and has a third salt concentration different from the second salt concentration. The concentrated flow is discharged from the first reservoir. The concentrated flow includes a fourth salt concentration that is less than the first and third salt concentrations, and a second solute concentration that is greater than the first solute concentration.

[0006] The above summary is not intended to describe each of the disclosed embodiments or all practices of this disclosure. The drawings and the following detailed description illustrate exemplary embodiments more specifically. [Brief explanation of the drawing]

[0007] The following discussion refers to the following figures, and the same reference numbers can be used to identify similar / identical components in multiple figures. However, the use of numbers to refer to components in a given figure is not intended to limit components in other figures labeled with the same number. The drawings are not necessarily to scale. [Figure 1]This is a diagram of a redox flow electrochemical solvent removal stack and system according to an exemplary embodiment. [Figure 2] This is a diagram of a redox flow electrochemical solvent removal stack and system according to another exemplary embodiment. [Figure 3] This figure shows the connection of multiple solvent removal stacks to a processing system according to an exemplary embodiment. [Figure 4] This figure shows the connection of multiple solvent removal stacks to a processing system according to an exemplary embodiment. [Figure 5] This is a flowchart of the method according to a specific embodiment. [Modes for carrying out the invention]

[0008] A system and method for removing water from a supply logistics by electrochemically removing a solute (e.g., salt) from the supply logistics using a combination of forward osmosis and electroosmosis is described. The supply logistics can be optionally concentrated with the same, different, or any combination thereof of the existing solute in the supply logistics before being introduced into the electrochemical salt removal system. In Figure 1, the figure shows an electrochemical liquid regenerator 100 illustrating the movement of fluids and ions in various embodiments. The electrochemical device 150 includes two electrodes 116, 118, at least three ion exchange membranes 110, 112, 114, an energy supply unit 152, a reaction mixture, and a containment fluid.

[0009] The first electrode 116 is configured to contact a first solution of the first redox-active electrolyte material and to have a first reversible redox reaction with the first redox-active electrolyte material. The second electrode 118 is configured to contact a second solution of the second redox-active electrolyte material and to have a second reversible redox reaction with the second redox-active electrolyte material. For simplicity, the first and second redox-active electrolyte materials are shown in Figure 1 as a redox shuttle solution 117 containing the redox-active electrolyte materials.

[0010] An example of a redox shuttle solution is 1,1'-bis((3-trimethylammonio)propyl)ferrocene([BTMAP-Fc] 2+ ) and 1,1'-bis((3-trimethylammonio)propyl)ferrocerium([BTMAP-Fc] 3+ ), or 1,1'-bis((3-dimethylethylammonio)propyl)ferrocene ([BDMEAP-Fc] 2+ ) and 1,1'-bis((3-dimethylethylammonio)propyl)ferrocerium([BDMEAP-Fc] 3+ )(These are non-toxic, very stable, have very rapid electrochemical kinetics and negligible membrane permeability), or ferrocyanides / ferricyanides ([Fe(CN)6] 4- / [Fe(CN)6] 3- For example, further details regarding additional redox shuttle solutions can be found in U.S. Patent Application No. 17 / 390,600, filed July 30, 2021, of the same owner (Agent Reference Number 20210171US01 / 0600.382US01), which is incorporated herein by reference in its entirety.

[0011] The redox shuttle 117 circulates between two electrodes 116, 118, as shown by the loop 154. When a potential is applied to each electrode 116, 118 by the energy supply unit 152, the redox shuttle is oxidized at the first electrode (e.g., 116) and reduced at the opposite electrode (e.g., 118). The energy supply unit 152 can be any variety of direct current (DC) energy supply units, such as a battery, photovoltaic panel, galvanic cell, potentiostat, or AC / DC power converter, the polarity may be kept the same overall or periodically reversed, and the energy supply unit may be contained within the electrochemical device 150 or be external and coupled to the device 150. Thus, as the shuttle 117 circulates between the electrodes, a portion of the shuttle 117 is continuously alternating between redox states. In certain embodiments, each electrode 116, 118 may be in contact with a separate redox active solution instead of the same redox shuttle solution 117 flowing through the loop. The separate redox active solution may have the same redox active electrolyte material or a different redox active electrolyte material. When different redox active solutions are used for each electrode 116, 118, the energy supply unit may periodically reverse the potential supplied to the electrodes to restore the respective charge state of the redox active electrolyte material solution (i.e., the proportion of the redox active electrolyte material in each solution that is in an oxidized state compared to a reduced state).

[0012] Positioned between electrodes 116 and 118 are three or more ion-exchange membranes that alternate in the form of ion exchange. For example, among the three membranes, as shown in Figure 1, the central membrane 110 may be a cation-exchange membrane sandwiched between the anion-exchange membranes of the second membrane 112 and the third membrane 114. However, in other embodiments, the central first membrane may be an anion-exchange membrane, and the second and third membranes may be cation-exchange membranes. The membranes 110, 112, and 114 define channels or reservoirs within the electrochemical device 150. As can be seen, the first membrane 110 and the second membrane 112 define a first reservoir 106, which in this example is configured as a desalination chamber. The first membrane 110, in combination with the third membrane 114, also defines a second reservoir 108, which in this example is configured as a salinate (or concentrate) channel. Membranes 110, 112, and 114 are ion-selective and water-permeable, insoluble in organic solvents, and inert (e.g., chemically unchangeable) in the reaction mixture and / or products. In certain embodiments, the membranes are as thin as possible (e.g., 10–50 μm) to maximize the rate of forward water transport through the membrane. In certain embodiments, the membranes are reinforced with a polymer mesh integrated into the membrane itself, while in other embodiments, the membranes are not reinforced.

[0013] The supply stream 102 is fed into the first reservoir 106 of the electrochemical device 150. The supply stream 102 contains at least a solvent (water in this example) and a salt having a first salt concentration (about 5 wt% in this example) (NaCl in this example, but also Na2SO4, CaCl2, KCl, and any other ionic salts in the chemical definition of “salt”). The supply stream 102 also contains a solute at the first solute concentration, the solute being different from the salt. In this example, the solute is a sugar at a concentration of about 12%, and can be any type of sugar or a combination thereof (e.g., sucrose, fructose, dextrose, etc.). Other solutes may include food solutes or particles, waste products, buffers, amino acids, salts different from the salt used in brine stream 122, catalysts used to facilitate chemical reactions in the supply stream, glycerol, ethylene glycol, etc. The brine stream 122 is fed into the second reservoir 108 of the electrochemical device 150. The brine stream has a second salt concentration (approximately 20%) that is higher than the first concentration. A portion of the concentrated brine 130 is optionally mixed with the supply stream 102 as the supply stream 102 enters the first reservoir 106 of the electrochemical device 150.

[0014] When an electric potential is applied to electrodes 116 and 118, the redox shuttle 117 is oxidized at one electrode 116 and reduced at the other electrode 118, thereby transporting salt ions 127 from the supply flow 102 in the first reservoir 106 to the brine flow 122 in the second reservoir 108. In particular, the redox shuttle 117 at the first electrode 116 receives at least one ion 134 from the salt in the first reservoir 106. The redox shuttle 117 at the second electrode 118 delivers at least one ion 133 into the brine flow 122 in the second reservoir 108, and the charge is equilibrated by delivering at least one ion 127 with the opposite sign of charge to ions 133 and 134 from the supply flow 102 in the first reservoir 106, across the central membrane 110, into the brine flow 122 in the second reservoir 108.

[0015] As ions 127 move from the first reservoir 106 to the second reservoir 108, they also drag solvent molecules (e.g., water 125) along with them across the central membrane 110 in a phenomenon known as electroosmosis. The water 125 also leaves the first reservoir 106 and enters the second reservoir 108 via forward osmosis, because the brine solution 122 in the second reservoir 108 has a higher osmotic pressure than the supply flow 102 and therefore also behaves as an inductive solution. As a result, the effluent flow 123, containing water 125 and a third salt concentration, is discharged from the second reservoir 108. In this case, the concentration of the effluent flow 123 is less than or equal to the concentration of the input brine flow 122, for example, the former may be 15-20% while the latter is 20%. Depending on the ratio of salt to water being transported, this flow will have a greater volume (or flow rate) but may or may not be diluted in concentration. It should be noted that the term “spillover” as used herein and elsewhere is for illustrative purposes only and is not limiting. In some cases, flows described as spilllover may be reused, retained, reprocessed, etc., and may have some value of their own as part of an overall fluid handling system. In other cases, spilllover flows may be disposed of as waste products.

[0016] Processing of the supply logistics 102 through the first reservoir 106 results in a concentrated logistics 144 exiting the first reservoir 106. The concentrated logistics 144 from the first reservoir contains a fourth salt concentration (e.g., less than 0.05%) which is less than the first, second, and third salt concentrations. The concentrated logistics 144 also has a higher concentration of solute than the supply logistics 102, e.g., 70% in the former and 12% in the latter. The net result is the transport of water from the supply logistics 102 to the brine solution 122. The effluent logistics 123 is regenerated (recovered to its original concentration and volume) using one or more of the various possible methods, as shown by the device 124, also referred to herein as a liquid concentrator. The effluent logistics 123 may be regenerated thermally in the device 124 by evaporating the absorbed water, by reverse osmosis, or electrochemically using electrodialysis or yet another electrochemical device using a redox shuttle. The emissions from device 124 are mainly water or the main solvent in the supply logistics 102, which is the emissions logistics 126.

[0017] The effluent logistics 123 can also be regenerated in the same electrochemical stack (or a series of identical stacks) once the solvent has been removed from the supply logistics. In Figure 2, the figure shows a redox-assisted solvent removal stack 200 that includes brine regeneration features according to another exemplary embodiment. The device 200 includes a first reservoir 106, supply logistics 102, second reservoir 108, brine flow 122, first electrode 116, second electrode 118, redox-activated electrolyte material shuttle 117, first reservoir 106, second reservoir 108, first membrane 110, second membrane 112, third membrane 114, effluent logistics 123, and concentrated logistics 144, similar to those shown and described in Figure 1. The stack 200 also includes other components not shown for clarity, such as an energy supply unit 152.

[0018] In this example, the first and second membranes 110 and 112 have a first set of electroosmotic and osmotic transport properties. The third membrane 114 has a second set of electroosmotic and osmotic transport properties, different from the first set of properties. The system 200 further includes a third reservoir 202 defined by the second membrane 112, and a fourth membrane 204 having a first ion exchange type (in this example, the same type as the first membrane 110, CEM). The fourth membrane 204 also has a second set of electroosmotic and osmotic transport properties. A second portion 206 of the brine flow 122 is fed into the third reservoir 202.

[0019] The fourth reservoir 208 is defined by a fourth membrane 204 and a fifth membrane 210 having a second ion exchange type (AEM in this example) and a second set of electroosmotic and osmotic transport properties. A third portion 212 of the brine solution 122 is introduced into the fourth reservoir 208. A second effluent flow 214 containing the solvent and a fifth salt concentration is discharged from the third reservoir 202. The solvent moves from the first and fourth reservoirs 106, 208 to the third reservoir 202 via electroosmosis and forward osmosis. A solvent flow 216 with a sixth salt concentration is discharged from the fourth reservoir 208.

[0020] Stack 200 enables brine regeneration by adding a pair of opposite-type (anion-to-cation or cation-to-anion) ion exchange membranes 114, 204 on the opposite side of a pair of membranes 110, 112 bounded by the supply logistics 102. The outer pair of ion exchange membranes 114, 204 are selected to have a second set of electroosmotic and osmotic transport properties different from those of the inner pair of ion exchange membranes 110, 112. A fifth membrane 210 also has these second electroosmotic and osmotic transport properties and is included to obtain the desired ion exchange with the redox shuttle 117 at the first electrode 116. The supply logistics 102 flows into reservoir / chamber 106 bounded by the inner pair of ion exchange membranes 110, 112, and the brine solution 122 flows into the remaining reservoirs / chambers 108, 202, 208. The membrane is arranged such that a reservoir / chamber 208, bounded by two membranes having low electroosmotic and osmotic transport properties, forms another desalination chamber. A portion of the brine solution 212 entering this chamber is thereby desalinized with minimal water loss to form a solvent stream 216 (water stream) exiting the electrochemical stack 200. The net result is a single stack that receives a diluted feed stream and discharges two streams: a concentrated product stream 144 and a water / solvent stream 216 with a very low salt content (e.g., both less than 0.05%).

[0021] The electrochemical stacks described above can be combined in various ways depending on the scale of the process and / or the desired amount of solvent removal. In FIG. 3, the figure shows a parallel stack arrangement according to an exemplary embodiment. The dilution feed reservoir 300 is coupled to the manifold 302 or other fluid distribution path and supplied to two or more electrochemical stacks 304, 305. If the stacks 304, 305 are configured as shown in FIG. 1, they may each have a dedicated salt regeneration device (see device 124) or share a single (commonly connected) salt regeneration device. The concentrated streams 306, 307 of the stacks 304, 305 are sent to the concentrate reservoir 308 for use or downstream processing or may be discharged, for example, as a waste stream. The solvent streams 310, 311 are discharged but may also be retained in a reservoir, holding tank, etc. for use or downstream processing. The system shown in FIG. 3 can utilize other inputs including electricity to drive the electrochemical reactions within the stacks 304, 305 and can drive fluid pumps (not shown) known in the art.

[0022] In FIG. 3, the figure shows a series stack arrangement according to an exemplary embodiment. The dilution supply reservoir 400 provides a feed stream 402 to a first electrochemical stack 404 connected in series to a second electrochemical stack 405. If stacks 404, 405 are configured as shown in FIG. 1, they may each have a dedicated salt regeneration device (see device 124) or may share a single salt regeneration device. The concentrated stream 406 of the first stack 404 is supplied to the second stack 405 as a feed stream, which discharges its own concentrated stream 407 having a solute at a higher concentration than the concentrated stream 406. The solvent streams 410, 411 are discharged but may also be retained in a reservoir, holding tank, etc. for use in downstream processing. If stacks 404, 405 are configured as shown in FIG. 1, they may each have a dedicated salt regeneration device (see device 124) or may share a single salt regeneration device. The system shown in FIG. 4 may utilize other inputs including electricity to drive the electrochemical reactions within stacks 404, 405 and may drive fluid pumps (not shown) known in the art. Note that the parallel and series arrangements shown in FIGS. 3 and 4 may be combined.

[0023] In FIG. 5, the flowchart shows a method for separating a solvent from a feed vapor according to an exemplary embodiment. The method involves introducing a feed stream having a first salt concentration into a first reservoir defined by a first ion exchange membrane and a second ion exchange membrane of an electrochemical cell (500). The second ion exchange membrane is a different type of membrane than the first ion exchange membrane. A second fluid stream having a second salt concentration higher than the first salt concentration is introduced into a second reservoir of the electrochemical cell (501). The second reservoir is defined by the first ion exchange membrane and a third ion exchange membrane. The third ion exchange membrane and the second ion exchange membrane are of the same type (e.g., AE or CE).

[0024] An external voltage is applied to the first and second electrodes of the electrochemical cell (502), and the solution containing the redox active electrolyte material circulates between the first and second electrodes (503). The redox active electrolyte material is reduced upon contact with the first electrode and oxidized upon contact with the second electrode. In response to the reduction and oxidation of the redox active electrolyte material, ions are transported across the first, second, and third ion exchange membranes to remove the solvent and salt from the first reservoir. Fluid flow having a third salt concentration less than or equal to the second salt concentration is discharged from the second reservoir (505). Concentrated flow having a fourth salt concentration less than the first and third salt concentrations is discharged from the first reservoir (506).

[0025] Unless otherwise indicated, all numbers used in this specification and the claims to represent feature sizes, quantities, and physical properties should be understood in all cases to be modified by the term “approximately.” Therefore, unless otherwise indicated, the numerical parameters described in the foregoing specification and the appended claims are approximations that may vary depending on the desired properties that a person skilled in the art would seek to obtain using the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5), as well as any range within that range.

[0026] The foregoing description is provided for illustrative and explanatory purposes only. It is not intended to be exhaustive or to strictly limit the embodiments to those disclosed. Many modifications and variations are possible in light of the above teachings. Any or all features of the disclosed embodiments can be applied individually or in any combination and are not intended to be limiting, but are merely illustrative. The scope of the invention is not intended to be limited to these “modes for carrying out the invention,” but rather to be determined by the “claims” appended herein.

Claims

1. 1. An electrochemical system comprising: a first reservoir containing a feed stream, the feed stream comprising a solvent, a salt having a first salt concentration in the feed stream, and a solute different from the salt at a first solute concentration; a second reservoir containing a brine stream, the brine stream having a second salt concentration greater than the first salt concentration; a first electrode in contact with a first solution of a first redox active electrolyte material, having a first reversible redox reaction with the first redox active electrolyte material, and configured to accept first ions from the salt in the first reservoir; a second electrode in contact with a second solution of a second redox active electrolyte material and having a second reversible redox reaction with the second redox active electrolyte material and configured to deliver second ions to the brine stream in the second reservoir; an energy source configured to supply an electrical potential to the first and second electrodes; a first membrane having a first ion exchange type disposed between the first reservoir and the second reservoir; a second membrane having a second ion exchange type different from the first ion exchange type, disposed between the first electrode and the first reservoir; a third membrane having the second ion exchange type disposed between the second electrode and the second reservoir; an effluent stream comprising the solvent and a third salt concentration discharged from the second reservoir, the solvent being removed from the first reservoir via electroosmosis and forward osmosis; and a concentrate stream discharged from the first reservoir, the concentrate stream comprising a fourth salt concentration that is less than the first, second, and third salt concentrations, and a second solute concentration that is greater than the first solute concentration.

2. The system of claim 1 , wherein the electroosmosis involves salt ions dragging molecules of the solvent out of the first reservoir through the first and second membranes.

3. 10. The system of claim 1, wherein the forward osmosis results from the brine stream in the second reservoir having a higher osmotic pressure than the feed stream in the first reservoir.

4. The system of claim 1 , wherein the fourth salt concentration is less than 0.05% by weight.

5. The system of claim 1 , wherein the solute comprises a sugar.

6. The system of claim 1 , wherein the solvent is water.

7. 2. The system of claim 1, wherein the first solution and the second solution are the same, and when an electric charge is applied to the electrodes, the first and second solutions circulate between the first electrode and the second electrode.

8. 2. The system of claim 1, wherein the first reservoir, the second reservoir, the first type membrane, and the second type membrane form a cell, and the system comprises a plurality of cells coupled together between the first electrode and the second electrode.

9. The system of claim 1 , wherein a portion of the brine stream is provided to the first reservoir.

10. 10. The system of claim 1, further comprising a liquid concentrator coupled to the effluent stream and configured to regenerate the brine stream and produce a waste stream comprising the solvent.

11. The system of claim 10 , wherein the liquid concentrator is an electrochemical liquid regenerator that utilizes a redox shuttle.

12. the first membrane and the second membrane have a first set of electroosmotic and osmotic transport properties, the third membrane has a second set of electroosmotic and osmotic transport properties that are different from the first set of properties, and the system comprises: a third reservoir defined by the second membrane and a fourth membrane having the first ion exchange type and the second set of electroosmotic and osmotic transport properties, wherein a second portion of the brine stream is input into the third reservoir; and a fourth reservoir defined by the fourth membrane and a fifth membrane having the second ion exchange type and the second set of electroosmotic and osmotic transport properties, wherein a third portion of the brine stream is input into the fourth reservoir; a second effluent stream comprising the solvent and a fifth salt concentration discharged from the third reservoir, the solvent migrating from the first and fourth reservoirs to the third reservoir via electroosmosis and forward osmosis; The system of claim 1 , further comprising: a solvent stream comprising a sixth salt concentration discharged from the fourth reservoir.

13. 13. The system of claim 12, wherein the effluent stream and the second effluent stream are combined and recycled as the brine stream input to the second, third, and fourth reservoirs.

14. 13. The system of claim 12, wherein the first, second, third, and fourth reservoirs and the first, second, third, and fourth membranes form a regeneration cell, and the system comprises a plurality of regeneration cells coupled together by the fourth membrane of a first regeneration cell and the third membrane of a second regeneration cell that defines the fourth reservoir of the first regeneration cell.

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