Electrochemical system and process for oxygen removal from a fluid
The electrochemical system with a proton exchange membrane and redox additives efficiently removes dissolved oxygen from fluids, addressing inefficiencies in existing methods by achieving low oxygen concentrations with reduced energy consumption and no chemical introduction.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-13
- Publication Date
- 2026-04-09
AI Technical Summary
Existing methods for removing dissolved oxygen from fluids, such as thermal fluids, are inefficient and often introduce harmful chemicals or require high energy consumption, failing to achieve low oxygen concentrations without chemical additives.
An electrochemical system using a proton exchange membrane and redox additives, with electrodes connected to a voltage source, facilitates the specific removal of oxygen through half-reactions, avoiding the introduction of chemicals and reducing energy costs.
The system effectively achieves very low dissolved oxygen concentrations comparable to chemical degassing without additives, reducing energy costs and minimizing unwanted reactions.
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Abstract
Description
AREA OF TECHNOLOGY
[0001] The present disclosure relates to the degassing of fluids and liquids, the electrochemical removal of oxygen from fluids and the removal of oxygen in thermal fluids. GENERAL STATE OF THE ART
[0002] The presence of dissolved oxygen in water and other solvents used in chemistry, biochemistry, biology, and medicine is often a complication, as it triggers undesirable chemical side reactions. This is a primary challenge for the pharmaceutical, food and beverage, and electronics industries, since dissolved oxygen can oxidize some organic or inorganic molecules and alter the chemistry of these industries' processes and products. An additional benefit is that oxygen removal also prevents corrosion of metal parts that come into contact with the purified water, as dissolved oxygen also initiates the oxidation of metal.
[0003] Common techniques for addressing the problem of high dissolved oxygen concentrations include thermal degassing, vacuum degassing, membrane degassing, absorption-based degassing, and vapor stripping degassing. With all these techniques, the removed gas is not specific to the removal of dissolved O₂ alone, but also to the removal of dissolved CO₂ and N₂. Each technique has its limitations and typically does not achieve very low dissolved oxygen concentrations, such as 10–100 µg / L. Only chemical degassing is specific to the removal of O₂ and can achieve very low dissolved oxygen concentrations, such as 1 µg / L. Chemical degassing is achieved by adding reducing agents to the solution, which then react with O₂. These reducing agents are irritating, sometimes toxic, affect the pH and hardness of the solution, and may need to be removed from the water later.
[0004] There is a need for alternative solutions to specifically remove dissolved oxygen from a fluid in order to achieve low concentrations of dissolved oxygen without the addition of chemical agents. SUMMARY
[0005] One object of the invention is to remove oxygen from a fluid electrochemically.
[0006] This was achieved, according to the present disclosure, by an electrochemical system for removing oxygen from a fluid. The system comprises a first electrode arranged in a first fluid; a second electrode designed to be in contact with a second fluid, the system being designed to remove oxygen from the second fluid; and a redox additive arranged in the first fluid, configured to switch between a loaded state RAH. xand to switch to a depleted state RA, with the redox additive in the loaded state RAH x is designed to be electrochemically oxidized to the depleted state RA; and a proton exchange membrane designed to separate the first fluid and the second fluid and configured to allow protons to move through the proton exchange membrane. The electrodes are connected to a voltage source arranged to provide a difference in electrical potential between the electrodes. When the electrode surfaces are in contact with each respective fluid and exhibit a potential difference between the electrode surfaces, the system causes a first half-reaction, RAH x → RA + xe - + xH + at the first electrode surface (111) and a second half-reaction O2 + 4e - +4H + → 2H2O at the second electrode surface, thereby removing oxygen from the second fluid.
[0007] This has the advantage of enabling the specific removal of dissolved oxygen, rather than CO2 or N2, leading to a reduction in energy costs for oxygen degassing compared to other processes designed to remove all gases. It also avoids the introduction of redox additives into the second fluid. The chemicals added to the first fluid do not need to be compatible with the second. Furthermore, this method allows for efficient oxygen removal, achieving very low dissolved oxygen concentrations comparable to those obtained through chemical degassing, without introducing any chemicals into the purified fluid.
[0008] In some embodiments, the first electrode comprises a first catalyst designed to charge the redox additive in the loaded state RAH. x to oxidize to the depleted state RA.
[0009] In some embodiments, the second electrode includes a second catalyst designed to catalyze the reduction of oxygen molecules to form water via hydrogen peroxide.
[0010] This has the advantage of reducing the electrical energy required for oxygen removal. It can also allow electrochemical reactions to be carried out with a lower potential drop at the electrodes, thereby reducing the number of unwanted reactions at the electrodes.
[0011] In some embodiments, the system further includes the voltage source, which is designed to generate a difference in electrical potential between the electrodes.
[0012] In some embodiments, the system further includes a redox additive replenisher designed to regenerate depleted redox additive RA in the first fluid and / or loaded redox additive RAH. x to add to the first fluid.
[0013] This has the advantage that the system continues to work even after the reduction of the original redox additive in the fluid.
[0014] In some embodiments, the system further comprises a fluid measuring device designed to measure oxygen in the second fluid and / or redox additive in the first fluid to form a set of measured values that include the concentration values of oxygen and / or redox additive, and wherein the voltage source and / or redox additive re-supplier is controlled based on the set of measured values.
[0015] In some embodiments, the system includes a computer connected to the voltage source, the redox additive replenishment system, the fluid transport means and / or the fluid measuring means, wherein the computer is configured to - Receiving potential and / or current information from the voltage source, and / or - Receiving the set of measured values, including the oxygen and / or redox additive concentration values, from the fluid measuring device; and the computer is configured to control the voltage source, redox additive replenishment device and / or the fluid transport device based on the received potential and / or current information and / or the set of measured values, including the oxygen and / or redox additive concentration values.
[0016] This has the advantage that the system can adjust the applied potential and replenish the redox additive based on the measured values. This can also have the advantage that oxygen can be removed with lower electrical energy consumption.
[0017] Use of the system according to claim 1 for removing oxygen from fluid in a closed-circuit fluid handling system and / or an open-circuit fluid handling system.
[0018] The present disclosure further relates to an electrochemical process for removing oxygen from a fluid. The process comprises: - Providing a first fluid with redox additive, wherein the redox additive is configured to switch between a loaded state RAH x and to switch to a depleted state RA in the first fluid, with the redox additive in the loaded state RAH x is designed to be electrochemically oxidized to the depleted state RA; - Providing a second fluid that includes the oxygen to be removed, - Providing a proton exchange membrane to the fluids, designed to separate the first fluid and the second fluid, with the proton exchange membrane configured to allow protons to move between the fluids; - Providing a first electrode on the first fluid and a second electrode on the second fluid, the electrodes being connected to a voltage source designed to apply a potential between the electrodes; - Applying an electrical potential between the electrodes, causing a first half-reaction, RAH x → RA + xe - + xH + at the first electrode surface (111) and a second half-reaction O2 + 4e - +4H + → 2H2O at the second electrode surface, thereby removing oxygen from the second fluid.
[0019] In some embodiments, the method further comprises measuring a set of measured values relating to the fluids comprising the oxygen concentration in the second fluid, and / or determining the rate of oxygen removal and controlling the applied electrical potential based on the set of measured values.
[0020] In some embodiments, the method further includes replenishing the depleted redox additive RA in the first fluid and / or adding redox additive in the loaded state RAH. x to the first fluid.
[0021] In some embodiments, the replenishment of redox additive and / or the applied electrical potential is based on the set of measured values. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 schematically shows an electrochemical system for removing oxygen from a fluid. Fig. Figure 2 schematically shows an electrochemical system for removing oxygen, arranged in a closed circuit with thermal fluid. Fig. Figure 3 schematically shows an electrochemical system for removing oxygen from a fluid. DETAILED DESCRIPTION
[0022] In all figures, the same reference symbols refer to the same parts, concepts, and / or elements. Therefore, what is stated regarding a reference symbol in one figure applies equally to the same reference symbol in other figures, unless explicitly stated otherwise.
[0023] Terms and Expressions: The term "dissolved oxygen," DO, refers to the concentration of dissolved oxygen in a fluid or liquid. One specific fluid of importance is water, which typically contains up to 9 ppm DO at room temperature and atmospheric pressure while in contact with the atmosphere.
[0024] The term "removal of oxygen" refers to the removal of free oxygen molecules from a fluid. For example, oxygen molecules, protons, and electrons can form water molecules in a half-reaction; in this case, the oxygen atoms are still present in the fluid, as contained in water molecules, but free oxygen molecules are removed.
[0025] The term "redox additive" refers to a molecule added to a fluid. This redox additive is configured to readily oxidize at the anode, thus counteracting the reduction of oxygen at the cathode in contact with the fluid containing the oxygen to be removed.
[0026] The term "redox additive" in a loaded state RAH x refers to a redox additive designed to be electrochemically oxidized to a depleted state RA by the removal of x protons, H +The additive molecules are preferentially released to release protons at the anode, thus compensating for the proton consumption at the cathode and converting O₂ to 2H₂O. It is generally important to maintain a constant pH of the liquid during the oxygen removal process, as both acidic and alkaline solutions would promote different types of corrosion. It is important to understand that the state of a specific redox additive can be pH-dependent, and the choice of redox additive is typically based on the expected pH range of the fluid.
[0027] The phrase "catalyzing the reduction of oxygen to form water via hydrogen peroxide" refers to the complex reduction of oxygen in an aqueous medium. Oxygen can undergo either a 2-electron reduction with the addition of 2 protons to yield H₂O₂ or a 4-electron reduction with the addition of 4 protons to yield 2H₂O. In this context, a catalyst for oxygen reduction is considered good if it drives the 4-electron / 4-proton reaction to H₂O. A poor catalyst would be more likely to provide the 2-electron / 2-proton reaction to hydrogen peroxide, H₂O₂.
[0028] The term "voltage source" refers to the means designed to apply an electrical electromotive force between the two electrodes of the system. The anode undergoes oxidation, and the cathode undergoes release. In an example oxygen removal system, dissolved oxygen at the cathode is removed by reduction, which is triggered either by a good catalyst on the cathode surface to form H₂O or by a poor catalyst on the cathode surface to form H₂O₂. The term "electrode surface" refers to the portion of the electrode that is accessible to the relevant fluid.
[0029] The term "energy costs" refers to the total electrical energy the system uses to remove dissolved oxygen from one liter of liquid. A reference fluid for degassing is, for example, water at atmospheric pressure containing 8.8 mg / L of dissolved oxygen at room temperature.
[0030] Fig. Figure 1 schematically shows an exemplary electrochemical system 100 for removing oxygen from a fluid. The system comprises a pair of electrodes 110 and 120, wherein the first electrode 110 is arranged in contact with a first fluid 130 and the second electrode 120 is designed to come into contact with a second fluid 140. The system 100 is designed to remove oxygen from the second fluid 140. The system further comprises a proton exchange membrane 150, which is designed to separate the first fluid 130 and the second fluid 140 and is configured to allow protons to move through the proton exchange membrane 150.
[0031] For example, the second fluid 140 can be part of a thermal fluid in a closed circuit. Typically, the oxygen to be removed is oxygen dissolved in a liquid, such as water.
[0032] The system further comprises a redox additive arranged in the first fluid 130. In some examples, the redox additive can be at least partially in a charged state, RAH2, wherein the redox additive in the charged state, RAH2, is designed to be oxidized to the depleted state, RA, by electrochemistry. The oxygen removal system 100 for the second fluid 140 is designed such that the redox additive in the first fluid 130 cannot enter the second fluid 140, but can participate in electrochemical half-reactions at the first electrode 110 with corresponding half-reactions at the second electrode 120 with charged protons that can move through the proton exchange membrane 150. Herein, the same reference number is used for the first fluid 130 as such, the first fluid 130 at the first electrode 110, and the first fluid 130 flowing towards and away from the first electrode 110.Accordingly, the same reference number is used for the second fluid 140.
[0033] Typically, during operation of system 100, there are flows of fluid 130 and 140 through system 100, entering system 100 via an inlet and exiting via an outlet. It is understood that system 100 can be used without fluid 130 and 140 flowing past electrodes 110 and 120; however, the use of active transport to remove oxygen in the second fluid 140, and the delivery of redox additives in a loaded state to the first fluid 130 and electrodes 110 and 120, can significantly improve oxygen removal. Fig. 1 and Fig. Figure 2 shows example systems 100, which are arranged under the assumption that a flow of fluids 130, 140 is provided, however these example systems 100 are able to remove oxygen from the second fluid 140 up to a certain capacity, even without a flow of fluids 130, 140 being provided.
[0034] Fig. Figure 1 shows the first fluid 130 and the second fluid 140 flowing through a part of the system 100, showing that two regions of fluid 131, 141 move towards the region between electrodes 110, 120, and two corresponding regions of fluid 132, 142 move out of between electrodes 110, 120. Typically, the regions of fluid 131, 141 moving towards the electrode pair 110, 120 form an inlet leading into a part of the system 100, and the regions of fluid 132, 142 moving away from the electrode pair 110, 120 form an outlet for a part of the system 100.
[0035] In some examples, the first fluid 130 is a liquid. In some of these examples, the first fluid 130 is an aqueous solution. In some examples, the second fluid 140 is a liquid. In some of these examples, the second fluid 140 is an aqueous solution.
[0036] It should be noted that the electrodes and fluid flow paths do not correspond to those in Fig. The flow configuration shown in Figure 1 is limited. The flow of fluids can be in a flow configuration for any type of electrode, where the flow path lies within the electrodes and runs longitudinally along the electrodes. The flow of fluids can also be in a flow configuration for any type of electrode, where the flow path lies partially within the electrodes and runs in a direction perpendicular to the electrodes; this would be the case for electrodes such as those shown in Figure 1. Fig. The electrodes are arranged in 1, corresponding to a flow from left to right. The flow of fluids 130, 140 can be a combination of bypass, flow-through, and cross-flow. It is also noted that the distance shown between the electrodes 110, 120 and the thickness of the electrodes 110, 120 in Fig. 1 are chosen for illustration purposes; for example, in some embodiments it may be advantageous to minimize the distance between the electrodes 110, 120.
[0037] Fig. Figure 1 shows the fluids 130, 140 in the region of the flow 131, 141, which move towards the region between the electrode surfaces 111, 121, while containing the redox additive RAH2 and oxygen, O2, respectively. The redox additive is in a charged state, RAH2, and is designed such that protons and electrons can be readily stripped into a depleted state RA by electrochemistry. After containing the fluids 130, 140 and applying a potential difference between the electrode surfaces 111, 121, the system 100 causes a first half-reaction, Eq. 1, at the first electrode surface 111 and a second half-reaction, Eq. 2, at the second electrode surface 121. RAH2 → RA + 2e - +2H + Eq. 1 O2 + 4e - +4H + → 2H2O Eq. 2
[0038] Fig. Figure 1 shows the fluids 130 and 140 exiting the area between the electrode surfaces 111 and 121 via the outlets 132 and 142, each containing a water molecule, the redox additive, and H₂O, respectively. The redox additive is in a depleted state, RA. The difference between the fluids 130 and 140 at the inlet 131 and outlet 132 indicates that oxygen has been reduced to water and that the redox additive has been oxidized according to equations 1 and 2.
[0039] In Fig. Figure 1 represents the redox additive RAH2 in the loaded state of example system 100, a molecule with two easily removable hydrogen atoms. It is noted that a redox additive in a loaded state RAH xin general can have two or another positive integer easily removable hydrogen atoms, where x is the number of easily removable hydrogen atoms, as shown in the general form of the first half-reaction equation 3. RAH x → RA + xe - + xH + Eq. 3
[0040] In some examples, the redox additive in the loaded state RAH2 is not oxidized to a soluble RA molecule. In some of these examples, the redox additive in the loaded state RAH2 is oxidized and polymerized to a polymer that is contained in the first electrode 110 and / or in the first fluid 130. In such examples, the redox additive in the loaded state RAH2 is removed from the first fluid 130 and / or deposited during oxygen removal from the first electrode. This allows the first fluid 130 of the system 100 to be regenerated by replacing the first electrode, which is coated with this electrolytically deposited polymer, with a new first electrode and adding fresh redox additive in the loaded state RAH2 to the first fluid 130.This is in comparison to examples where the redox additive in the loaded state RAH2 is added to the first fluid 130 and the redox additive in the depleted state RA can simply accumulate in the first fluid 130.
[0041] In some examples, the depleted redox additive RA is removed from the first fluid 130 and / or regenerated to the loaded redox additive RAH2. In some of these examples, the system 100 includes a redox additive replenisher (not shown) designed to regenerate the depleted redox additive RA from the first fluid 130 to the loaded redox additive RAH2 and / or to add the loaded redox additive RAH2 to the first fluid 130.
[0042] Typically, under the conditions where the second half-reaction, Eq. 2, takes place at the second electrode 120 and the second fluid 140, oxygen and protons can also undergo the reaction to produce hydrogen peroxide, H₂O₂, via an alternative second half-reaction, Eq. 4. Hydrogen peroxide is an oxidizing agent and is typically undesirable in the second fluid 140, from which oxygen is removed; therefore, the second electrode 120 and / or a second catalyst are ideally selected to carry out the reaction according to Eq. 2 with minimal production of hydrogen peroxide by the reaction according to Eq. 4. In an alternative or complementary approach, the second electrode 120 and / or the second catalyst can be configured to facilitate the conversion of hydrogen peroxide to water, so that produced and unwanted hydrogen peroxide can be neutralized by the system 100. O2 + 2e - +2H +→ H2O2 Eq. 4
[0043] The example electrodes 110, 120 in Fig. 1 each comprise a layer of conductive polymer and a back-contact electrode 112, 122. Typically, a back-contact electrode has a higher conductivity than the material of the electrode between the back-contact electrode and the corresponding electrode surface 111, 121, in order to better utilize the entire electrode surface 111, 121.
[0044] The electrodes 110, 120 are connected to a voltage source 160, which is arranged such that a difference in electrical potential is created between the electrodes 110, 120.
[0045] In some examples, the system includes the voltage source 160.
[0046] In some examples, the voltage source 160 is designed to monitor, record, and / or transmit the current through the electrodes 110, 120 and / or the potential applied to them. For example, by analyzing the current and / or potential, the amount of oxygen removed from the second fluid 140, the amount of oxygen remaining in the second fluid 140, and / or the amount of redox additive in a loaded state in the first fluid 130 can be estimated. The electrodes 110, 120 each comprise an electrode surface 111, 121, which is designed to be in contact with the first fluid 130 and the second fluid 140, respectively.
[0047] It is noted that the system can include a plurality of first electrodes 110 and a plurality of second electrodes 120. Fluid paths between inlets 131, 141 and outlets 132, 142 can pass by several pairs of electrodes 110, 120 to increase the probability that dissolved oxygen and redox additives undergo electrochemical reactions at the electrodes 110, 120.
[0048] In some examples, the first electrode 110 and the second electrode 120 are at most 100 mm apart. In some of these examples, the first electrode 110 and the second electrode 120 are separated by at most 50 mm, at most 10 mm, at most 2 mm, at most 200 µm, or at most 50 µm. For example, if porous electrodes 110, 120 are used that are designed to allow a flow of fluids 130, 140, it may be desirable to position the electrodes 110, 120 as close as possible to the proton exchange membrane 150, so that the electrodes 110, 120 are essentially separated by the thickness of the proton exchange membrane 150.
[0049] In some examples, the electrodes 110, 120 are arranged on the proton exchange membrane 150.
[0050] In some examples, the proton exchange membrane 150 comprises a perfluorinated sulfonic acid membrane, copoly(arylene ether) comprising superacid groups, a carboxylated or sulfonated nanocellulose membrane and / or a phosphoric acid-doped polybenzimidazole membrane.
[0051] In some examples, the proton exchange membrane 150 comprises an alkylsulfonated aromatic polymer electrolyte membrane. In some of these examples, the proton exchange membrane 150 comprises at least one sulfonated derivative of the following aromatic polymers: poly(styrene), poly(oxy-1,4-phenylenoxy-1,4-phenylenecarbonyl-1,4-phenylene), poly(1,4-phenylene), poly(oxy-1,4-phenylene), and poly(phenylene sulfide).
[0052] In some examples, the system includes the reaction chamber with inlets 131, 141 and outlets 132, 142, wherein the electrodes 110, 120 are arranged in the reaction chamber and the reaction chamber is designed to accommodate the first fluid 130 and the second fluid 140 for oxygen removal.
[0053] In some examples, the system 100 comprises a plurality of pairs of the first electrode 110 and the second electrode 120. In some of these examples, the number of pairs of the first electrode 110 and the second electrode 120 is at least 3, at least 5, at least 10, at least 20 or at least 50.
[0054] It should be noted that the electrodes 110, 120 and the flow path of the fluids 130, 140 past and / or through the electrodes 110, 120 can be arranged in a number of ways, depending on factors such as acceptable energy costs, flow capacity, and the amount of oxygen removed per unit fluid flow. Generally, it is desirable to minimize the distance between the electrodes 110, 120 and maximize the contact between the fluids 130, 140 and the electrodes, for example, by having fluid 130, 140 flow through porous electrodes.
[0055] In some examples, the first and / or the second electrode 110, 120 comprise the back-contact electrode 112, 122. In some of these examples, the back-contact electrode 112, 122 comprises conductive polymer, carbon, metal, and / or metal oxide. In some examples, a plurality of electrodes 110, 120 are arranged in a sandwich configuration with alternating first electrodes 110 and second electrodes 120.
[0056] In some examples, the first and / or the second electrode 110, 120 is a porous electrode. In some of these examples, the first and / or second electrode 110, 120 has a specific surface area of at least 10 m². 2 / g, at least 100 m 2 / g or at least 1000 m 2 / g. In some examples, the first and / or the second electrode 110, 120 is a porous electrode configured to allow the corresponding fluid 130, 140 to flow through the electrode 110, 120.
[0057] It is noted that a porous electrode, allowing fluid to flow through it, can enable a very small distance between the electrodes, while a significant portion of the fluid flow may be within the electrodes, compared to the flow in the volume between the electrodes.
[0058] In some examples, the first electrode 110 comprises conductive polymer, carbon, metal and / or metal oxide.
[0059] In some examples, the first and / or the second electrode comprises 110, 120 poly(3,4-ethylenedioxythiophene), PEDOT.
[0060] In some examples, the first electrode 110 is configured such that, after oxidation of the redox additive in the loaded state RAH2, it binds the oxidized redox additive to the first electrode 110.
[0061] In some examples, the first electrode 110 is designed to be an interchangeable first electrode 110.
[0062] In some examples, the first electrode 110 includes a first catalyst (not shown) designed to oxidize the redox additive in the loaded state RAH2.
[0063] In some of these examples, the first catalyst comprises a conductive polymer, carbon, metal, and / or metal oxide. In other examples, the first catalyst comprises a microporous structure and / or a surface functionalized with strong acid groups. Polymer catalysts can, for example, provide highly reversible, selective, and fast proton-coupled electron transfer reactions, such as the oxidation of RAH2 according to Eq. 3 by polystyrenesulfonic acid in combination with PEDOT.
[0064] It is noted that, in order to ensure a low operating voltage, there are two large voltage drops, one due to the resistance across the membrane and the other due to the overpotential at the electrodes. The overpotential can be reduced by using a catalyst. The catalyst can be placed on the electrode or as a layer of catalytic material directly on one side of the proton exchange membrane 150 to minimize the distance between the electrodes 110 and 120. Such a catalytic layer can act as an extension of the electrodes 110 and 120 directly on the surface of the membrane 150.For example, a catalytic layer can be obtained by creating a coating on the membrane consisting of a slurry made of catalytic nanoparticles mixed with a conducting matrix, carbon black, or a conductive polymer. The entire composite can be held together by a polymer binder that acts as both a binder and a proton conductor, typically an ionomer such as Nafion. For porous electrodes designed to allow fluid flow through them, it may then be sufficient to position the catalyst on the membrane and in physical contact between the catalytic layer and the porous electrode, so that the catalytic layer becomes an electrical extension of the electrode.In such an example, most of the reaction usually takes place at the catalytic layer due to the catalyst, while the other part of the porous electrode reacts less strongly because there is no catalyst in the electrode.
[0065] In some examples, the system 100 includes a first catalyst arranged in physical and / or electrical contact with the first electrode 110. In some of these examples, the first catalyst is arranged at the proton exchange membrane 150.
[0066] In some examples, the second electrode comprises 120 conductive polymer, carbon, metal and / or metal oxide.
[0067] In some examples, the second electrode surface 121 comprises a catalyst designed to carry out the second half-reaction, Eq. 2. In some of these examples, the second catalyst is designed to selectively form water via hydrogen peroxide. In some examples, the second catalyst comprises a composite of noble metal, non-noble metal, nitrogen, and carbon (MNC). In some of these examples, the second catalyst comprises cobalt phthalocyanine, metal porphyrin, pyrolyzed organic nitrogen-containing molecules with Fe salts, and / or graphitic carbon nitride-coordinated transition metals. In some examples, the second catalyst comprises an oxynitride and / or a non-noble metal oxide. In some of these examples, the second catalyst includes MnO2, Mn3O4, Co3O4, TiO2, NbO2, TaOxNy, MnOOH, Ni(OH)2, Co(OH)2, ZnO, fluorinated tin oxide, FTO) and / or chalcogenides such as Co9S8 or CoSe2.
[0068] In some examples, the system 100 includes a second catalyst arranged in physical and / or electrical contact with the second electrode 120. In some of these examples, the second catalyst is arranged on the proton exchange membrane 150.
[0069] It should be noted that the term “half-reaction at the first or second electrode surface” also refers to the half-reaction that occurs at the first or second catalyst in physical contact and / or electrical contact with the corresponding electrode 110, 120.
[0070] In some examples, the first half-reaction occurs at the first catalyst and / or the second half-reaction occurs at the second catalyst.
[0071] In some examples, the second catalyst comprises platinum, Pt3M alloys (M = Ti, V, Fe, Co, Ni), or Pt5M alloys (M = Tm, Dy, Tb, Gd, Sm, Ca, Ce, La). In some of these examples, the second catalyst comprises palladium, silver, iridium, copper, nickel, vanadium, molybdenum, and / or alloys thereof in the form of nanoclusters and / or in metal-heteroatom-doped carbon.
[0072] In some examples, the second catalyst comprises an n-doped conductive polymer. In some of these examples, the second catalyst comprises poly(benzimidazobenzophenanthroline), BBL, and / or poly(benzodifuranedione), PBFDO. In some examples, the second electrode 120 is designed to facilitate the conversion of all produced H₂O₂ to H₂O. In some of these examples, the second electrode 120 is made of iron and facilitates the conversion of H₂O₂ to H₂O. In most cases, it is desirable to minimize the amount of oxygen and hydrogen peroxide leaving the system 100.
[0073] In some examples, the second electrode 120 comprises an Fe compound and a porous carbon and / or a conductive polymer and is designed to facilitate the conversion of all produced H2O2 to H2O.
[0074] In some examples, the loaded redox additive RAH2 is organic or inorganic. In other examples, the loaded redox additive RAH2 is a soluble redox polymer or insoluble redox nanoparticles. The redox additives are designed to be oxidized upon oxygen reduction. The potential difference between the reduction potential of oxygen and the oxidation potential of the loaded redox additive RAH2 depends on the energy used to remove the oxygen, ideally minimizing this energy cost. The required potential difference relates to two phenomena: (i) the intrinsic redox potential of the species, which depends on its chemical structure and HOMO level; and (ii) any overpotential that presents a kinetic barrier to the reaction, such overpotentials typically arising from the lack of a suitable catalyst for the reactions.In some examples, the redox additive in the loaded state RAH2 is designed to dissociate in the first fluid 130, such as tiron-forming mobile ions in water. This can reduce the resistance of the first fluid 130 and the voltage that needs to be applied between the electrodes 110, 120, thereby reducing the energy cost of oxygen removal. In some examples, the ion concentration in the first and / or second fluid 130, 140 is increased by the addition of species.
[0075] In some examples, the redox additive has a size that cannot pass through an intact proton exchange membrane. In some examples, the redox additive has a molecular weight of at least 200 g / mol in both the loaded and depleted states. In some of these examples, the molecular weight is at least 100 g / mol, at least 50 g / mol, or at least 30 g / mol. The system is generally designed so that redox additives are never released into the second fluid during normal operation.
[0076] In some examples, the redox additive comprises an oligomer, a polymer chain, a nanoparticle, a microparticle, or a suspension of particles.
[0077] In some examples, the redox additive is covalently linked to an oligomer or polymer without redox activity, so that the functionalized oligomer or polymer becomes redox-active.
[0078] In some examples, the redox additive is encapsulated, chemisorbed, or absorbed in or on porous conductive particles. In some of these examples, the porous conductive particles include activated carbon and / or carbon black.
[0079] In some examples, the redox additive comprises conductive polymers, redox polymers, nanoparticles, and / or particles with a size of at least in the micrometer range. In some examples, the redox additive is non-toxic.
[0080] In some examples, the redox additive comprises aromatic monomers. In some of these examples, the redox additive includes thiophene, dibenzothiophene, 3,4-ethylenedioxythiophene, pyrrole, furan, and / or derivatives thereof.
[0081] In some examples, the redox additive comprises an organic molecule configured to be readily oxidized by proton-coupled electron transfer. In some of these examples, the redox additive includes an organic aromatic non-alcohol such as tyrosine, or organic aromatic diols such as ortho-benzodiols or catechol and / or more soluble derivatives thereof such as tiron, alizarin red, or para-benzodiols such as hydroquinone and / or derivatives thereof such as 2,5-dihydroxy-3,6-dimethyl-1,4-benzoquinone. In some examples, the redox additive includes soluble oligomers and / or polymers of quinones such as polycatechols and / or lignosulfonates. In some examples, the redox additive includes metal hydride complexes, phenazine and / or phenothiazine dyes such as methylene blue and neutral red.A useful value for an oxygen removal system is the energy required to reduce the concentration of dissolved oxygen in water under ambient conditions from 8-9 mg / l to 0.1 mg / l, or more preferably 0.01 mg / l, for a given volume of water, expressed as energy per volume. One approach to reducing the energy cost could be to increase the ion concentration in the first and / or second fluid 130, 140 to decrease the resistance between the electrodes 110, 120.
[0082] In some examples, the System 100 is designed to reduce the concentration of dissolved oxygen in water at room temperature and atmospheric pressure from 8-9 mg / l to a maximum of 0.1 mg / l. In some of these examples, the concentration of dissolved oxygen in the water is reduced to a maximum of 0.01 mg / l or a maximum of 0.001 mg / l. In some of these examples, the energy cost for reducing the concentration of dissolved oxygen is a maximum of 0.5 Wh / l or a maximum of 0.05 Wh / l.
[0083] It should be noted that the best choice for the second electrode 120 and / or the second catalyst for the efficient execution of the reaction according to Eq. 2 may not be the best choice under certain conditions if very low hydrogen peroxide production is desired. The best choice of electrodes and redox additive generally depends on the conditions, the desired concentration of dissolved oxygen, and the tolerance regarding energy costs and hydrogen peroxide production.
[0084] In some examples, the system 100 is designed to add an antioxidant molecule to the second fluid 140 and / or to provide the antioxidant molecule at the second electrode 120, the antioxidant molecule being designed to react with any unwanted radicals formed during the electrochemical reactions. In some of these examples, the antioxidant molecule comprises flavonoids.
[0085] In some examples, the system 100 comprises a housing (not shown) with fluid inlets 131, 141 and fluid outlets 132, 142, wherein the housing includes the first and second electrodes 110, 120, which are arranged on fluid paths between the fluid inlets and outlets 131, 141, 132, 142. In some of these examples, the system comprises the first fluid 130 and the redox additive in the first fluid 130. In some of these examples, the system comprises a closed fluid that includes the first fluid 130. In some of these examples, the system 100 comprises a fluid transport means designed to provide movement of the first fluid 130 at the first electrode 110. In some of these examples, the fluid transport means is designed to provide a continuous flow of the first fluid 130 at the first electrode 110.In some of these examples, the system 100 includes a fluid measuring device (not shown) designed to regenerate depleted redox additive to loaded redox additive in the first fluid 130 and / or to add loaded redox additive to the first fluid 130.
[0086] It is noted that in some embodiments of the system 100, the first fluid 130 and the structures comprising the first fluid 130 are part of the system 100, while the second fluid 140 is outside the system 100, and the system 100 is designed to be arranged on the second fluid 140. In some examples, the system 100 comprises an internal container with the first fluid 130, the fluid transport and redox additive replenishment agent, and the system 100 is arranged on an external fluid infrastructure comprising the second fluid 140 and is configured to remove oxygen from the second fluid 140.
[0087] In some examples, the system 100 includes a computer, the voltage source 160, the fluid measuring device and / or a redox additive after-supplier.
[0088] In some examples, the system 100 comprises the computer connected to the voltage source 160, the redox additive replenishment system and / or the fluid measuring device designed to measure a set of measurements related to the fluids 130, 140, the computer being configured to: - Receiving potential and / or current information from voltage source 160, and / or - Receiving the set of measured values, including the oxygen and / or redox additive concentration values, from the fluid measuring device; and the computer is configured to control the voltage source 160 and / or the redox additive after-supplier based on the received potential and / or current information and / or the set of measured values, including the oxygen and / or redox additive concentration values.
[0089] In some examples, the fluid measuring device is designed to measure the concentration of dissolved oxygen in the second fluid by applying a maximum potential difference of 1.5 V between the electrodes for a maximum of 20 seconds and determining the dissolved oxygen concentration based on the resulting current. In some of these examples, a maximum potential difference of 1 V between the electrodes is applied for a maximum of 10 seconds.
[0090] It is noted that the use of redox additives in the first fluid and the application of electrochemistry enable the System 100 to function as both an oxygen remover and an oxygen concentration detector. By first using the system as an oxygen concentration detector to determine an oxygen concentration, its subsequent operation as an oxygen remover can then be optimized. In some examples, the System 100 continuously determines the oxygen concentration while operating as an oxygen remover based on this determined concentration. In other examples, the System 100 is integrated into infrastructure, such as piping, designed to allow the second fluid 140 to flow through the infrastructure, with the second fluid 140 containing the oxygen to be removed.
[0091] It is noted that the system 100, which comprises a voltage source 160 and a computer designed to calculate a dissolved oxygen concentration based on potential and / or current information from the voltage source 160, can function as a dissolved oxygen concentration sensor system. In some examples, the system includes a dissolved oxygen concentration sensor system designed to detect dissolved oxygen concentrations below 0.1 mg / l.
[0092] Fig. Figure 2 schematically shows an example of an electrochemical system 200 for oxygen removal, comprising a first fluid containing redox additives, wherein the system 200 is arranged in a closed circuit 300, and the second fluid is a thermal fluid. The example oxygen removal system 200 includes an oxygen remover 100, a redox additive replenisher 210, and a fluid transport means 220 designed to move the first fluid at the first electrode, for example, a pump.
[0093] The exemplary closed circuit 300 comprises pipes 340 containing thermal fluid with oxygen to be removed, a pump 320 designed to transport thermal fluid through the closed circuit, a heat load 310 from which heat is to be removed, and a heat exchanger 330 designed to conduct heat away from the second fluid of the closed circuit and connected to the oxygen remover 100. For example, the heat exchanger 330 may introduce dissolved oxygen into the second fluid, and the dissolved oxygen must be kept at low concentrations to avoid significant corrosion in the closed circuit 200.
[0094] The oxygen remover 100 can be an oxygen remover 100 according to one of the in relation to Fig. The examples described in 1 are examples. It is noted that the electrochemical system 200 for removing oxygen may be contained in a housing, with the components and piping of the electrochemical system 200 for removing oxygen being arranged on or in the oxygen remover 100. Although in Fig. 2 where the electrochemical system 200 is shown for illustrative purposes with separate components connected by fluid piping, it may typically be advantageous to arrange the system 100 in a device that is located on the second fluid from which oxygen is to be removed.
[0095] In some examples, the oxygen remover 100 comprises a housing with fluid inlets 131, 141 and fluid outlets 132, 142 for the first and second fluid respectively, wherein the housing includes the first and second electrodes 110, 120.
[0096] It is noted that the oxygen removal system 100 can be arranged on the closed circuit 200 such that a portion of the total volume of the second fluid flows through the oxygen removal system 100, thus preventing the total flow through the closed circuit 300 from being limited by the capacity of the oxygen removal system. For example, a flow rate of 100 l / s can be circulated through the closed circuit 300, while 10 l / s can be directed through the oxygen removal system 100.
[0097] In some examples, the system is arranged in a closed loop of a second fluid and is designed to remove oxygen from the second fluid. In some of these examples, the closed loop is intended for thermal fluids.
[0098] In some examples, the oxygen removal system 200 further includes the redox additive replenisher 210, which is designed to regenerate depleted redox additive in the first fluid and / or to add redox additive to the first fluid. Fig. 2 The redox additive after-supplier 210 is arranged upstream of the main unit of the oxygen remover 100. In some examples, the redox additive after-supplier 210 is connected to the oxygen remover 100, and the oxygen remover 100 is configured to control the redox additive after-supplier 210.
[0099] In some examples, the system 200 includes a fluid measuring device 230 designed to measure a set of measurements relating to the first fluid, and includes a computer designed to control the redox additive refiller 210 so that redox additive in the loaded state RAH xthe thermal fluid is added based on the set of measured values. In some of these examples, the oxygen remover 100 includes the fluid measuring device 230. In some of these examples, the fluid measuring device 230 is designed to measure the set of measured values, where the set of measured values relates to the second fluid. For example, a fluid measuring device 230 arranged at the oxygen remover 100 can measure both the first and the second fluid; alternatively, the fluid measuring device 230 can measure the second fluid at the inlet 141 and / or the outlet 142 of the second fluid.
[0100] In some examples, the fluid measuring device 230 is designed to measure or monitor the current and / or potential applied by the voltage source. In some examples, the fluid measuring device 230, or at least a part of it, is contained within the voltage source of the oxygen remover 100.
[0101] In some examples, the fluid measuring device 230 is designed to measure a set of measurements for at least one of the following: current and potential applied by the voltage source; concentration of dissolved oxygen in the second fluid; concentration of redox additive in the first fluid for the loaded state RAH2 and / or the depleted state RA; pH, temperature, and pressure in the first and / or second fluid; and amount of electrodeposited redox additive at the first electrode. In some of these examples, the computer is designed to control the applied potential and / or current of the voltage source and / or the redox additive replenisher 210 based on the measurements received by the fluid measuring device 230.
[0102] In some examples, the oxygen remover 100 comprises a housing with fluid inlets 131, 141 and fluid outlets 132, 142, wherein the housing includes the first and second electrodes 110, 120. In some of these examples, the housing includes the voltage source, the fluid measuring device 230, a redox additive refiller 210 and / or the computer.
[0103] In some examples, the system includes the computer connected to the voltage source, the redox additive replenishment unit 210, the fluid transport unit 220 and / or the fluid measuring unit 230, with the computer being configured to: - Receiving potential and / or current information from the voltage source, and / or - Receiving the set of measured values, including the oxygen and / or redox additive concentration values, from the fluid measuring device 230; and wherein the computer is configured to control the voltage source, the fluid transport device 220 and / or the redox additive after-supplier 210 on the basis of the received potential and / or current information and / or the set of measured values, including the oxygen and / or redox additive concentration values.
[0104] In some examples, the system 200 includes a main memory (not shown) connected to the computer, and the computer is designed to store and retrieve information from the voltage meter and / or the fluid measuring device 230.
[0105] Fig. Figure 3 schematically shows an electrochemical system for removing oxygen from a fluid. The process 400 comprises: - Providing 410 of a first fluid with redox additive, wherein the redox additive is configured to switch between a loaded state RAH x and to switch to a depleted state RA in the first fluid, with the redox additive in the loaded state RAH x is designed to be electrochemically oxidized to the depleted state RA; - Provide 420 of a second fluid comprising the oxygen to be removed, - Providing 430 of a proton exchange membrane to the fluids, designed to separate the first fluid and the second fluid, the proton exchange membrane being configured to allow protons to move between the fluids; - Providing 440 a first electrode on the first fluid and a second electrode on the second fluid, the electrodes being connected to a voltage source designed to apply a potential between the electrodes; - Applying an electrical potential of 450 between the electrodes causes a first half-reaction, Eq. 3, at the first electrode surface and a second half-reaction, Eq. 2, at the second electrode surface, thereby removing oxygen from the second fluid. RAH x → RA + xe - + xH + Eq. 3 O2 + 4e - +4H + → 2H2O Eq. 2
[0106] In some examples, providing 440 electrodes includes providing at least one electrode comprising a catalyst for the first half-reaction, Eq. 3, and / or the second half-reaction, Eq. 2.
[0107] In some examples, providing a first fluid with redox additive involves repeatedly moving the first fluid at the first electrode. In some of these examples, providing a first fluid with redox additive involves providing a continuous flow of the first fluid at the first electrode. Typically, the mass transport of the second fluid to the first electrode is carried out by an external infrastructure.
[0108] In some examples, the procedure further includes measuring a set of measurements relating to the fluids. In some of these examples, measuring includes calculating the concentration of dissolved oxygen in the second fluid and / or the rate of oxygen removal from the second fluid and controlling the applied electrical potential based on the set of measurements that include the calculated concentration of dissolved oxygen and / or the rate of oxygen removal.
[0109] In some examples, measuring 460 of the set of measurements includes measuring the redox additives in the first solution in the loaded and / or depleted state.
[0110] In some examples, the procedure further includes replenishing the redox additive by regenerating the redox additive in the quenched state in the first fluid and / or adding the redox additive in the loaded state to the first fluid. In some examples, the regeneration and / or addition of the redox additive is based on a set of measurements that include a calculated concentration of dissolved oxygen in the second fluid.
[0111] In some examples, the set of measured values includes values for at least one of the following: current and potential applied by the voltage source; concentration of dissolved oxygen in the second fluid; concentration of redox additive in the first fluid for the loaded state RAH2 and / or the depleted state RA; pH, temperature, and pressure in the fluids; and the amount of electrodeposited redox additive at the first electrode. In some of these examples, the application of an electrical potential, the transport of the first fluid to the first electrode, and / or the replenishment of redox additive are based on the set of measured values.
[0112] In some examples, the procedure involves measuring the set of measured values relating to the fluids using a fluid measuring instrument.
[0113] In some examples, the control of the applied 450 electrical potential is based on the calculated concentration of dissolved oxygen 460, furthermore on the set of measured values that include values for the current or potential applied by the voltage source and / or the concentration of redox additive in the first fluid for the loaded state RAH2 and / or the depleted state RA.
[0114] In some examples, Procedure 400 includes a step of determining an initial concentration of dissolved oxygen in the second fluid. In some of these examples, the calculation of the dissolved oxygen concentration is based on the determined initial concentration of dissolved oxygen. Determining an initial concentration can be of interest for second fluids in a closed loop.
[0115] In some examples, Procedure 400 includes a step of determining an initial concentration of redox additive in the loaded state in the first fluid. In some of these examples, the redox additive concentration is calculated based on an initial addition of redox additive to the first fluid.
[0116] In some examples, procedure 400 includes a step of measuring the concentration of redox additive in the loaded state in the first fluid and / or the concentration of redox additive in the depleted state in the first fluid. In some of these examples, the replenishment 470 of redox additive in the first fluid is based on the concentration of redox additive in the loaded and / or depleted state.
[0117] It is noted that the step of determining the initial concentration of dissolved oxygen and the step of determining the initial concentration of redox additive are generally related to establishing an initial state of the fluids before oxygen removal, while the step of measuring 460 of the set of measured values, which includes calculating the concentration of dissolved oxygen, controlling the applied potential and replenishing 470 of redox additive, is related to the steps carried out during or after oxygen removal.
Claims
[1] Electrochemical system (100; 200) for removing oxygen from a fluid, wherein the system (100; 200) comprises: - a first electrode (110) arranged on a first fluid (130), - a second electrode (120) designed to come into contact with a second fluid (140), wherein the system (100; 200) is designed to remove oxygen from the second fluid (140), - a redox additive arranged in the first fluid (130) configured to switch between a loaded state RAH x and to switch to a depleted state RA, with the redox additive in the loaded state RAH x is designed to be electrochemically oxidized to the depleted state RA, and - a proton exchange membrane (150) designed to separate the first fluid (130) and the second fluid (140) and configured to allow protons to move through the proton exchange membrane (150), wherein the electrodes (110, 120) are connected to a voltage source (160) arranged to create a potential difference between the electrodes (110, 120), and wherein the system (100; 200), when the electrode surfaces (111, 121) are in contact with each respective fluid (130, 140) and exhibit a potential difference between the electrode surfaces (111, 121), undergoes a first half-reaction, RAH x → RA + xe - + xH + at the first electrode surface (111) and a second half-reaction O2 + 4e - +4H + → 2H2O is caused on the second electrode surface (121), thereby removing oxygen from the second fluid (140). [2] System according to claim 1, wherein the first electrode (110) comprises a first catalyst designed to charge the redox additive in the loaded state RAH x to oxidize to the depleted state RA. [3] System according to claims 1 to 2, wherein the second electrode (110) comprises a second catalyst designed to catalyze the reduction of oxygen molecules to form water via hydrogen peroxide. [4] System according to any of the preceding claims, comprising a voltage source (160) arranged such that a difference in electrical potential is provided between the electrodes (110, 120). [5] System according to claim 1, comprising a redox additive replenisher (210) designed to regenerate depleted redox additive RA in the first fluid (130) and / or loaded redox additive RAH x to add to the first fluid (130). [6] System according to one of claims 4 to 5, comprising a fluid measuring device (230) designed to measure oxygen in the second fluid (140) and / or redox additive in the first fluid (130) to form a set of measured values comprising the concentration values of oxygen and / or redox additive, and wherein the voltage source (160) and / or the redox additive re-supplier (210) is controlled based on the set of measured values. [7] System according to any one of the preceding claims, comprising a fluid transport means (220) designed to transport the first fluid (130) to the first electrode (110). [8] System according to any one of claims 4 to 7, comprising a computer connected to the voltage source (140), the redox additive replenishment device (210), the fluid transport means (220) and / or the fluid measuring means (230), wherein the computer is configured to: - Receiving potential and / or current information from the voltage source (140), and / or - Receiving the set of measured values, including the oxygen and / or redox additive concentration values, from the fluid measuring device (230); and wherein the computer is configured to control the voltage source (140), the redox additive after-supplier (210) and / or the fluid transport device (220) on the basis of the received potential and / or current information and / or the set of measured values, including the oxygen and / or redox additive concentration values. [9] Use of the system (100; 200) according to any one of claims 1 to 8 for removing oxygen from fluid in a closed-circuit fluid handling system (300) and / or an open-circuit fluid handling system. [10] Electrochemical method for removing oxygen from a fluid, wherein the method (400) comprises: - Providing (410) a first fluid (130) with redox additive, wherein the redox additive is configured to switch between a loaded state RAH x and to switch to a depleted state RA in the arrangement in the first fluid (130), wherein the redox additive is in the loaded state RAH x is designed to be electrochemically oxidized to the depleted state RA; - Providing (420) a second fluid (140) comprising the oxygen to be removed, - Providing (430) a proton exchange membrane (150) to the fluids (130, 140) designed to separate the first fluid (130) and the second fluid (140), wherein the proton exchange membrane (150) is configured to allow protons to move between the fluids (130, 140); - Providing (440) a first electrode (110) at the first fluid (130) and a second electrode (120) at the second fluid (140), wherein the electrodes (110, 120) are connected to a voltage source (160) designed to apply a potential between the electrodes (110, 120); - Applying (450) an electrical potential between the electrodes (111, 121), thereby initiating a first half-reaction, Eq. RAH x → RA + xe - + xH + at the first electrode surface (111) and a second half-reaction O2 + 4e - +4H + → 2H2O is caused on the second electrode surface (121), thereby removing oxygen from the second fluid (140). [11] Method according to claim 10, comprising measuring (460) a set of measured values relating to the fluids (130, 140) comprising the oxygen concentration in the second fluid (140), and / or determining the rate of oxygen removal and controlling the applied (450) electrical potential based on the set of measured values. [12] Method according to claim 10 or 11, comprising replenishing (470) the depleted redox additive RA in the first fluid (130) and / or adding redox additive in the loaded state RAH x to the first fluid (130). [13] Method according to claims 11 and 12, wherein the replenishment (470) of redox additive and / or the applied (450) electrical potential is based on the set of measured values.