US20260159967A1
ACIDIFICATION OF SEAWATER IN AN ELECTROLYTIC - CATION EXCHANGE MODULE (E-CEM) DEVICE
Publication
Application
Classifications
IPC Classifications
CPC Classifications
Applicants
Evoqua Water Technologies LLC
Inventors
Li Shiang LIANG, Dhruti KUVAR
Abstract
An apparatus for generation of at least one of carbon dioxide or hydrogen from saline water is disclosed. The apparatus includes an anodic compartment, an anode on a first side of the anodic compartment, a cathodic compartment, a cathode on a first side of the cathodic compartment, a first cation permeable fluidic separator on a second side of the anodic compartment, a second cation permeable fluidic separator on a second side of the cathodic compartment, a center compartment between the first and second cation permeable fluidic separators, and a mixing chamber including an inlet fluidly connectable to or in fluid communication with the outlet of the anodic compartment and an outlet, the center compartment having one of an outlet fluidly connectable to or in fluid communication with the inlet of the mixing chamber or an inlet fluidly connectable to or in fluid communication with the outlet of the mixing chamber.
Figures
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001]This application claims priority under 35 U.S.C. § 119 (e) to U.S. Provisional Application Ser. No. 63/698,243, titled “ACIDIFICATION OF SEAWATER IN AN ELECTROLYTIC-CATION EXCHANGE MODULE (β-CEM) DEVICE,” filed on Sep. 24, 2024, the subject matter of same being incorporated herein by reference in its entirety for all purposes.
GOVERNMENT LICENSE RIGHTS
[0002]This invention was made with government support under Contract No. N00014-21-C-1019 awarded by the Department of the Navy. The government has certain rights in the invention.
FIELD OF TECHNOLOGY
[0003]Aspects and embodiments disclosed herein relate to devices and methods for acidifying seawater to generate and capture carbon dioxide (CO2) and hydrogen (H2).
SUMMARY
[0004]In accordance with one aspect, there is provided an apparatus for generation of at least one of carbon dioxide or hydrogen from saline water. The apparatus comprises an anodic compartment having an inlet and an outlet, an anode disposed on a first side of the anodic compartment, a cathodic compartment having an inlet and an outlet, a cathode disposed on a first side of the cathodic compartment, a first cation permeable fluidic separator disposed on a second side of the anodic compartment, a second cation permeable fluidic separator disposed on a second side of the cathodic compartment, a center compartment defined between the first cation permeable fluidic separator and the second cation permeable fluidic separator, and a mixing chamber including an inlet fluidly connectable to or in fluid communication with the outlet of the anodic compartment and an outlet, the center compartment having one of an outlet fluidly connectable to or in fluid communication with the inlet of the mixing chamber or an inlet fluidly connectable to or in fluid communication with the outlet of the mixing chamber.
[0005]In some embodiments, the outlet of the mixing chamber is fluidly connectable to or in fluid communication with the inlet of the center compartment.
[0006]In some embodiments, the apparatus further comprises a deoxygenation apparatus configured and arranged to at least partially deoxygenate anolyte from the outlet of the anodic compartment prior to the anolyte from the outlet of the anodic compartment being introduced into the mixing chamber.
[0007]In some embodiments, the apparatus further comprises a source of fresh saline water fluidly connectable to or in fluid communication with the inlet of the mixing chamber.
[0008]In some embodiments, the apparatus further comprises a controller configured to regulate relative amounts of the anolyte from the output of the anodic compartment and the fresh saline water that are mixed in the mixing chamber to form an acidic saline water with a predetermined pH.
[0009]In some embodiments, the predetermined pH of the acidic saline water is less than about 6. The predetermined pH of the acidic saline water may be in a range of pH 3 to 5.
[0010]In some embodiments, the apparatus further comprises a pH sensor disposed at the outlet of the anodic compartment and in communication with the controller.
[0011]In some embodiments, the controller is further configured to regulate a flow rate of anolyte through the anodic compartment at a rate which maintains a pH of the anolyte from the outlet of the anodic compartment at a predetermined value. The predetermined level of pH of the anolyte from the outlet of the anodic compartment may be in a range of pH 2 to 3.
[0012]In some embodiments, the inlet of the center compartment is fluidly connectable to or in fluid communication with the outlet of the mixing chamber.
[0013]In some embodiments, the apparatus further comprises a controller configured to regulate relative amounts of anolyte from the output of the anodic compartment, effluent from the center compartment, and the fresh saline water introduced into the mixing chamber to produce a mixed product stream having a pH of less than about 5. The pH of the mixed product stream may be in a range of pH 3 to 5.
[0014]In some embodiments, the source of fresh saline water is a source of seawater.
[0015]In accordance with another aspect, there is provided a method of facilitating generation at least one of hydrogen or carbon dioxide from seawater. The method comprises providing an electrolytic cell including an anodic compartment having an inlet and an outlet, an anode disposed on a first side of the anodic compartment, a cathodic compartment having an inlet and an outlet, a cathode disposed on a first side of the cathodic compartment, a first cation permeable fluidic separator disposed on a second side of the anodic compartment, and a second cation permeable fluidic separator disposed on a second side of the cathodic compartment, the center compartment defined between the first cation permeable fluidic separator and the second cation permeable fluidic separator. The method further comprises providing instructions to flow anolyte through the anodic chamber to form an acidified anolyte, and to introduce the acidified anolyte from the outlet of the anodic chamber and fresh seawater into a mixing chamber including an inlet in fluid communication with the outlet of the anodic compartment. The center compartment includes one of an outlet in fluid communication with the inlet of the mixing chamber or an inlet in fluid communication with the outlet of the mixing chamber.
[0016]In some embodiments, the method further comprises providing instructions to at least partially deoxygenate the anolyte from the outlet of the anodic chamber prior to introducing the anolyte from the outlet of the anodic chamber into the mixing chamber.
[0017]In some embodiments, the outlet of the mixing chamber is in fluid communication with the inlet of the center compartment and the method further comprises providing instructions to produce an acidified seawater from the anolyte from the outlet of the anodic chamber and the fresh seawater in the mixing chamber, and to flow the acidified seawater through the center compartment.
[0018]In some embodiments, the method further comprises providing instructions to remove hydrogen and carbon dioxide from the cathodic compartment and the center compartment, respectively.
[0019]In some embodiments, the method further comprises providing instructions to regulate relative amounts of the anolyte from the output of the anodic compartment and fresh seawater that are mixed in the mixing chamber to form the acidified seawater with a predetermined pH.
[0020]In some embodiments, the predetermined pH is less than about 6.
[0021]In some embodiments, the inlet of the mixing chamber is in fluid communication with the outlet of the center compartment and the method further comprises providing instructions to direct effluent from the outlet of the center compartment, anolyte from the outlet of the anodic compartment, and the fresh seawater into the mixing chamber to form a mixed product solution from which the carbon dioxide may be extracted.
[0022]In some embodiments, the method further comprises providing instructions to regulate relative amounts of the anolyte from the output of the anodic compartment, the effluent from the outlet of the center compartment, and the fresh saline introduced into the mixing chamber to produce the mixed product solution with a pH of less than about 5.
[0023]In accordance with another aspect, there is provided a method of retrofitting an apparatus for generation of at least one of carbon dioxide or hydrogen from a saline water source, the apparatus comprising an anodic compartment having an inlet and an outlet, a cathodic compartment having an inlet and an outlet, and a center compartment defined between the anodic compartment and the cathodic compartment. The method comprises connecting an inlet of a mixing chamber to the outlet of the anodic compartment, and one of connecting the outlet of the center compartment to the inlet of the mixing chamber or connecting an outlet of the mixing chamber to an inlet of the center compartment.
[0024]In some embodiments, the method further comprises fluidically connecting a source of fresh seawater to the mixing chamber.
[0025]In some embodiments, the method further comprises fluidically connecting an outlet of the mixing chamber to the inlet of the center compartment.
[0026]In some embodiments, the method further comprises fluidically connecting the outlet of the center compartment to the mixing chamber, fluidically connecting the outlet of the anodic compartment to the mixing chamber, and fluidically connecting a source of fresh seawater to the mixing chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027]The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in the various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
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DETAILED DESCRIPTION
[0042]The total carbon content of the world's oceans is approximately 38,000 gigatons (GT). Over 95% of this carbon is in the form of dissolved bicarbonate ion (HCO3−). This bicarbonate ion, along with the carbonate ion (CO32-), is responsible for buffering and maintaining the pH of the ocean which is relatively constant below the first 100 meters of ocean depth. The dissolved bicarbonate and carbonate ions present in the ocean are effectively bound CO2, and the sum of the concentrations of these species, along with dissolved gaseous CO2, represents the total carbon dioxide concentration [CO2]T, of seawater.
[0043]At a typical ocean pH of 7.8, kept relatively constant by a complex bicarbonate-carbonate buffer system, [CO2]T is about 2000 μmoles/kg near the surface and about 2400 μmoles/kg at depths below 300 meters. This equates to approximately 100 mg/L of [CO2]T. Of the total CO2 in the ocean, about 2-3% is dissolved gaseous CO2, about 1% is present as the dissolved carbonate ion, and the remainder, about 96%, is present as the dissolved bicarbonate ion. It is known that the equilibrium form and concentration of water containing CO2 and its various ionic forms is dependent on the pH of the water. For example, at a seawater pH of 4.5, 99% of all carbonate species in seawater exist as carbonic acid, H2CO3. Thus, to convert HCO3− to H2CO3, the pH of seawater may be lowered.
[0044]CO2 dissolved in water is in equilibrium with H2CO3 as shown in equation 1:
[0045]The hydration equilibrium constant is 1.70×10−3. This indicates that H2CO3 is not stable in water and gaseous CO2 readily dissociates at pH of 4.5, allowing CO2 to be easily removed by degassing or stripping once the seawater has been acidified to ensure that the unstable H2CO3 is deprotonated to the predominant carbonate species.
[0046]Electrochemical cells are used in marine, offshore, municipal, industrial, and commercial implementations. The design parameters of electrochemical cells, for example, inter-electrode spacing, thickness of electrodes and coating density, electrode areas, methods of electrical connections, etc., can be selected for different implementations. Aspects and embodiments disclosed herein are not limited to the number of electrodes, the space between electrodes, the electrode material, material of any spacers between electrodes, number of passes within the electrochemical cells, or electrode coating material.
[0047]An electrochemical device with ion exchange membranes can be designed to change the pH of a fluid stream while generating reaction products at the electrodes.

[0048]In addition, chlorine gas evolution is possible at the anode if the anolyte contains chloride ions:
[0049]In
[0050]Conversely, in
[0051]One use of the device in
[0052]The main reactions in the center (seawater) compartment are:

[0053]The pK1 and pK2 values are for seawater at 10° C. Other ions may react with the H+, such as conversion of borate to boric acid.
[0054]Seawater has a pH of ˜8.
[0055]The feeds to the anode and cathode compartments are conductive solutions, such as reverse osmosis (RO) product water with conductivity<200 μS/cm or sodium sulfate solution with conductivity of ˜200-3000 μS/cm.
[0056]
[0057]The present disclosure proposes a method to acidify the seawater feed and effluent in an Electrolytic—Cation Exchange Module (E-CEM) device.
- [0059]Flow compartment width: 1.25 in (3.18 cm)
- [0060]Flow compartment length: 7.0 in (17.8 cm)
- [0061]Electrode compartment thickness: 0.06 in (0.15 cm)
- [0062]Seawater compartment thickness: 0.375 in (0.95 cm) or 0.75 in (1.9 cm)
- [0063]Active membrane area: 8.75 in2 (56.45 cm2)
- [0064]Electrodes: Platinum coated titanium plate
- [0065]Membranes: Ionpure® heterogeneous CEM
[0066]Hereinafter, seawater compartment thickness of 0.375 inches will be referred to as “1× thickness” and thickness of 0.75 inches will be referred to as “2× thickness”. An example of a test run is shown in
- [0068]Seawater feed: synthetic Instant Ocean® seawater with conductivity of 49.05 mS/cm and HCO3 concentration of 194 ppm (higher than typical seawater)
- [0069]Anolyte and catholyte feed: 270 μS/cm Na2SO4 solution in deionized water
- [0070]Current density: 317 A/m2 (1.79 A)
- [0071]Anolyte flow rate: 0.15 l/min (residence time T=3.4 sec)
- [0072]Seawater flow rate: 0.30 l/min (residence time T=10.8 sec)
- [0073]Catholyte flow rate: 0.15 l/min (residence time T=3.4 sec)
[0074]
[0075]From the regression equations, the current density utilized at different residence times (or vice versa) to achieve a given steady state pH can be calculated.
[0076]
[0077]From the applied current the amount of H+ ions generated at the anodes (in mol/s) can be estimated for the test runs using the Faraday constant.
[0078]The pH of the anolyte effluent varies from 2.6-3.0, averaging around 2.8. Based on the reduction in pH from the inlet to the outlet and the flow rate, the amount of H+ ions used to reduce the pH in the anolyte can be estimated.
[0079]Calculations were used to estimate the amount of excess H+ ions that are “wasted” in the seawater compartment. The results are shown in
[0080]The overall indication is that a significant percentage of the H+ ions generated is underutilized, particularly as the residence time decreases. Aspects and embodiments disclosed herein include modifications of the E-CEM devices to increase the utilization rate and thereby reduce the energy consumption of the process in terms of kWh supplied from the DC power supply per mol of H2CO3 removed from seawater.
[0081]A first embodiment of an improved apparatus for generation of carbon dioxide and hydrogen from a saline water source (an E-CEM device) is illustrated generally at 100 in
[0082]In the E-CEM device 100, O2 gas in the anolyte effluent 160 is removed by vacuum, by membrane degasification or by purging with air, by a degasification/deoxygenation system 165 as shown in
[0083]The E-CEM device 100 may include a controller, for example, a general purpose computer, ASIC, PLC or other form of controller known in the art, configured to regulate relative amounts of the at least partially deoxygenated anolyte from the output 110B of the anodic compartment 110 and the fresh seawater 175 that are mixed to form the pre-acidified seawater feed 185 to maintain a predetermined pH of the pre-acidified seawater feed 185 using one or more pumps or valves (not shown so as not to obscure the figure).
[0084]A pH sensor pH may be disposed at the outlet 110B of the anodic compartment 110 (or in another location in a fluid line carrying the anolyte from the outlet 110B of the anodic compartment 110) and in communication with the controller. Another pH sensor pH may be disposed in a fluid line carrying the pre-acidified seawater feed 185. Communication lines to the controller are not illustrated so as not to complicate the figure. The controller may utilize measurements of pH of the anolyte from the outlet 110B of the anodic compartment 110 and/or measurements of the pH of the pre-acidified seawater feed 185 to determine how to regulate relative amounts of the at least partially deoxygenated anolyte from the output 110B of the anodic compartment 110 and the fresh seawater 175 that are mixed to form the pre-acidified seawater feed 185 to maintain the predetermined pH of the pre-acidified seawater feed 185. The controller may further regulate a flow rate of the anolyte through the anolyte chamber to provide the anolyte from the outlet 110B of the anodic compartment 110 with a predetermined pH. A desired range of pH for the anolyte effluent may be a pH range of 2-3 or a pH range of 1-2.
[0085]In a second embodiment, indicated generally at 200 in
[0086]In the E-CEM device 200, the controller is configured to regulate relative amounts of the seawater effluent 190, anolyte effluent 160, and fresh seawater 175 to mix in the mixing chamber 180 to produce the acidified seawater 195 with a predetermined pH, for example, based on readings from pH meter(s) on or within conduit(s) through which any one or more of the seawater effluent 190, anolyte effluent 160, and/or acidified seawater 195 passes.
[0087]Both E-CEM device embodiments 100, 200 benefit by reducing the total power consumption and reduced number of modules required for producing acidified seawater. This also lowers the footprint of the overall unit.
[0088]The present disclosure also contemplates a method of facilitating generation of at least one of hydrogen or carbon dioxide from seawater. The method includes providing an electrolytic cell including an anodic compartment having an inlet and an outlet, an anode disposed on a first side of the anodic compartment, a cathodic compartment having an inlet and an outlet, a cathode disposed on a first side of the cathodic compartment, a first cation permeable fluidic separator disposed on a second side of the anodic compartment, and a second cation permeable fluidic separator disposed on a second side of the cathodic compartment, the center compartment defined between the first cation permeable fluidic separator and the second cation permeable fluidic separator. The method further includes providing instructions to flow anolyte through the anodic chamber to form an acidified anolyte, and to introduce the acidified anolyte from the outlet of the anodic chamber and fresh seawater into a mixing chamber including an inlet in fluid communication with the outlet of the anodic compartment, the center compartment having one of an outlet in fluid communication with the inlet of the mixing chamber or an inlet in fluid communication with the outlet of the mixing chamber.
[0089]The method may further include providing instructions to at least partially deoxygenate the anolyte from the outlet of the anodic chamber prior to introducing the anolyte from the outlet of the anodic chamber into the mixing chamber.
[0090]In some embodiments, the outlet of the mixing chamber is in fluid communication with the inlet of the center compartment and the method further includes providing instructions to produce an acidified seawater from the anolyte from the outlet of the anodic chamber and the fresh seawater in the mixing chamber, and flow the acidified seawater through the center compartment.
[0091]The method may further include providing instructions to remove hydrogen and carbon dioxide from the cathodic compartment and the center compartment, respectively, and may further include providing instructions to regulate relative amounts of the anolyte from the output of the anodic compartment and fresh seawater that are mixed in the mixing chamber to form the acidified seawater with a predetermined pH.
[0092]The predetermined pH may be less than about 6.
[0093]In some embodiments, the inlet of the mixing chamber is in fluid communication with the outlet of the center compartment and the method further includes providing instructions to direct effluent from the outlet of the center compartment, anolyte from the outlet of the anodic compartment, and the fresh seawater into the mixing chamber to form a mixed product solution from which the carbon dioxide may be extracted.
[0094]The method may further include providing instructions to regulate relative amounts of the anolyte from the output of the anodic compartment, the effluent from the outlet of the center compartment, and the fresh saline introduced into the mixing chamber to produce the mixed product solution with a pH of less than about 5.
[0095]The present disclosure further contemplates a method of retrofitting an apparatus for generation of at least one of carbon dioxide or hydrogen from a saline water source, the apparatus comprising an anodic compartment having an inlet and an outlet, a cathodic compartment having an inlet and an outlet, and a center compartment defined between the anodic compartment and the cathodic compartment. The method includes connecting an inlet of a mixing chamber to the outlet of the anodic compartment, and one of connecting the outlet of the center compartment to the inlet of the mixing chamber or connecting an outlet of the mixing chamber to an inlet of the center compartment.
[0096]The method may further include fluidically connecting a source of fresh seawater to the mixing chamber.
[0097]The method may further include fluidically connecting an outlet of the mixing chamber to the inlet of the center compartment.
[0098]The method may further include fluidically connecting the outlet of the center compartment to the mixing chamber, fluidically connecting the outlet of the anodic compartment to the mixing chamber, and fluidically connecting a source of fresh seawater to the mixing chamber.
[0099]The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases “consisting of” and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims. Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
[0100]Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Any feature described in any embodiment may be included in or substituted for any feature of any other embodiment. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
[0101]Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments disclosed.
Claims
What is claimed is:
1. An apparatus for generation of at least one of carbon dioxide or hydrogen from saline water, the apparatus comprising:
an anodic compartment having an inlet and an outlet;
an anode disposed on a first side of the anodic compartment;
a cathodic compartment having an inlet and an outlet;
a cathode disposed on a first side of the cathodic compartment;
a first cation permeable fluidic separator disposed on a second side of the anodic compartment;
a second cation permeable fluidic separator disposed on a second side of the cathodic compartment;
a center compartment defined between the first cation permeable fluidic separator and the second cation permeable fluidic separator; and
a mixing chamber including an inlet fluidly connectable to or in fluid communication with the outlet of the anodic compartment and an outlet, the center compartment having one of an outlet fluidly connectable to or in fluid communication with the inlet of the mixing chamber or an inlet fluidly connectable to or in fluid communication with the outlet of the mixing chamber.
2. The apparatus of
3. The apparatus of
4. The apparatus of
5. The apparatus of
6. The apparatus of
7. The apparatus of
8. The apparatus of
9. The apparatus of
10. The apparatus of
11. The apparatus of
12. A method of facilitating generation at least one of hydrogen or carbon dioxide from seawater, the method comprising:
providing an electrolytic cell including:
an anodic compartment having an inlet and an outlet;
an anode disposed on a first side of the anodic compartment;
a cathodic compartment having an inlet and an outlet;
a cathode disposed on a first side of the cathodic compartment;
a first cation permeable fluidic separator disposed on a second side of the anodic compartment;
a second cation permeable fluidic separator disposed on a second side of the cathodic compartment, the center compartment defined between the first cation permeable fluidic separator and the second cation permeable fluidic separator; and
providing instructions to:
flow anolyte through the anodic chamber to form an acidified anolyte; and
introduce the acidified anolyte from the outlet of the anodic chamber and fresh seawater into a mixing chamber including an inlet in fluid communication with the outlet of the anodic compartment, the center compartment having one of an outlet in fluid communication with the inlet of the mixing chamber or an inlet in fluid communication with the outlet of the mixing chamber.
13. The method of
14. The method of
15. The method of
16. The method of
17. The method of
18. The method of
19. The method of
20. A method of retrofitting an apparatus for generation of at least one of carbon dioxide or hydrogen from a saline water source, the apparatus comprising an anodic compartment having an inlet and an outlet, a cathodic compartment having an inlet and an outlet, and a center compartment defined between the anodic compartment and the cathodic compartment, the method comprising:
connecting an inlet of a mixing chamber to the outlet of the anodic compartment; and
one of connecting an outlet of the center compartment to the inlet of the mixing chamber or connecting an outlet of the mixing chamber to an inlet of the center compartment.
21. The method of
22. The method of
23. The method of
fluidically connecting the outlet of the center compartment to the mixing chamber;
fluidically connecting the outlet of the anodic compartment to the mixing chamber; and
fluidically connecting a source of fresh seawater to the mixing chamber.